diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index b2f933e1194..349edf4b609 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -10651,15 +10651,7 @@ module ts {
                 return grammarErrorOnNode(parameter.name, Diagnostics.An_index_signature_parameter_must_have_a_type_annotation);
             }
             if (parameter.type.kind !== SyntaxKind.StringKeyword && parameter.type.kind !== SyntaxKind.NumberKeyword) {
-                if (parameter.type.kind === SyntaxKind.SymbolKeyword) {
-                    if (languageVersion < ScriptTarget.ES6) {
-                        return grammarErrorOnNode(parameter.type, Diagnostics.symbol_indexers_are_only_available_when_targeting_ECMAScript_6_and_higher);
-                    }
-                    // No error for parameter type
-                }
-                else {
-                    return grammarErrorOnNode(parameter.name, Diagnostics.An_index_signature_parameter_type_must_be_string_number_or_symbol);
-                }
+                return grammarErrorOnNode(parameter.name, Diagnostics.An_index_signature_parameter_type_must_be_string_or_number);
             }
             if (!node.type) {
                 return grammarErrorOnNode(node, Diagnostics.An_index_signature_must_have_a_type_annotation);
diff --git a/src/compiler/diagnosticInformationMap.generated.ts b/src/compiler/diagnosticInformationMap.generated.ts
index c491acdf2ef..9745f251e66 100644
--- a/src/compiler/diagnosticInformationMap.generated.ts
+++ b/src/compiler/diagnosticInformationMap.generated.ts
@@ -19,7 +19,7 @@ module ts {
         An_index_signature_parameter_cannot_have_an_initializer: { code: 1020, category: DiagnosticCategory.Error, key: "An index signature parameter cannot have an initializer." },
         An_index_signature_must_have_a_type_annotation: { code: 1021, category: DiagnosticCategory.Error, key: "An index signature must have a type annotation." },
         An_index_signature_parameter_must_have_a_type_annotation: { code: 1022, category: DiagnosticCategory.Error, key: "An index signature parameter must have a type annotation." },
-        An_index_signature_parameter_type_must_be_string_number_or_symbol: { code: 1023, category: DiagnosticCategory.Error, key: "An index signature parameter type must be 'string', 'number', or 'symbol'." },
+        An_index_signature_parameter_type_must_be_string_or_number: { code: 1023, category: DiagnosticCategory.Error, key: "An index signature parameter type must be 'string' or 'number'." },
         A_class_or_interface_declaration_can_only_have_one_extends_clause: { code: 1024, category: DiagnosticCategory.Error, key: "A class or interface declaration can only have one 'extends' clause." },
         An_extends_clause_must_precede_an_implements_clause: { code: 1025, category: DiagnosticCategory.Error, key: "An 'extends' clause must precede an 'implements' clause." },
         A_class_can_only_extend_a_single_class: { code: 1026, category: DiagnosticCategory.Error, key: "A class can only extend a single class." },
@@ -147,7 +147,6 @@ module ts {
         Merge_conflict_marker_encountered: { code: 1185, category: DiagnosticCategory.Error, key: "Merge conflict marker encountered." },
         A_rest_element_cannot_have_an_initializer: { code: 1186, category: DiagnosticCategory.Error, key: "A rest element cannot have an initializer." },
         A_parameter_property_may_not_be_a_binding_pattern: { code: 1187, category: DiagnosticCategory.Error, key: "A parameter property may not be a binding pattern." },
-        symbol_indexers_are_only_available_when_targeting_ECMAScript_6_and_higher: { code: 1188, category: DiagnosticCategory.Error, key: "'symbol' indexers are only available when targeting ECMAScript 6 and higher.", isEarly: true },
         Duplicate_identifier_0: { code: 2300, category: DiagnosticCategory.Error, key: "Duplicate identifier '{0}'." },
         Initializer_of_instance_member_variable_0_cannot_reference_identifier_1_declared_in_the_constructor: { code: 2301, category: DiagnosticCategory.Error, key: "Initializer of instance member variable '{0}' cannot reference identifier '{1}' declared in the constructor." },
         Static_members_cannot_reference_class_type_parameters: { code: 2302, category: DiagnosticCategory.Error, key: "Static members cannot reference class type parameters." },
diff --git a/src/compiler/diagnosticMessages.json b/src/compiler/diagnosticMessages.json
index e3f8a880111..fd09a49d3fb 100644
--- a/src/compiler/diagnosticMessages.json
+++ b/src/compiler/diagnosticMessages.json
@@ -67,7 +67,7 @@
         "category": "Error",
         "code": 1022
     },
-    "An index signature parameter type must be 'string', 'number', or 'symbol'.": {
+    "An index signature parameter type must be 'string' or 'number'.": {
         "category": "Error",
         "code": 1023
     },
@@ -579,11 +579,6 @@
         "category": "Error",
         "code": 1187
     },
-    "'symbol' indexers are only available when targeting ECMAScript 6 and higher.": {
-        "category": "Error",
-        "code": 1188,
-        "isEarly": true
-    },
 
     "Duplicate identifier '{0}'.": {
         "category": "Error",
diff --git a/tests/baselines/reference/arraySigChecking.errors.txt b/tests/baselines/reference/arraySigChecking.errors.txt
index 85948381ff5..b70b659773c 100644
--- a/tests/baselines/reference/arraySigChecking.errors.txt
+++ b/tests/baselines/reference/arraySigChecking.errors.txt
@@ -1,4 +1,4 @@
-tests/cases/compiler/arraySigChecking.ts(11,17): error TS1023: An index signature parameter type must be 'string', 'number', or 'symbol'.
+tests/cases/compiler/arraySigChecking.ts(11,17): error TS1023: An index signature parameter type must be 'string' or 'number'.
 tests/cases/compiler/arraySigChecking.ts(18,5): error TS2322: Type 'void[]' is not assignable to type 'string[]'.
   Type 'void' is not assignable to type 'string'.
 tests/cases/compiler/arraySigChecking.ts(22,1): error TS2322: Type 'number[][]' is not assignable to type 'number[][][]'.
@@ -20,7 +20,7 @@ tests/cases/compiler/arraySigChecking.ts(22,1): error TS2322: Type 'number[][]'
     
         var foo: { [index: any]; }; // expect an error here
                     ~~~~~
-!!! error TS1023: An index signature parameter type must be 'string', 'number', or 'symbol'.
+!!! error TS1023: An index signature parameter type must be 'string' or 'number'.
     }
     
     interface myInt {
diff --git a/tests/baselines/reference/genericTypeReferenceWithoutTypeArgument.d.errors.txt b/tests/baselines/reference/genericTypeReferenceWithoutTypeArgument.d.errors.txt
index 5d7da139c2b..6c98d419dec 100644
--- a/tests/baselines/reference/genericTypeReferenceWithoutTypeArgument.d.errors.txt
+++ b/tests/baselines/reference/genericTypeReferenceWithoutTypeArgument.d.errors.txt
@@ -2,7 +2,7 @@ tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenc
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument.d.ts(10,21): error TS2314: Generic type 'C<T>' requires 1 type argument(s).
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument.d.ts(11,22): error TS2314: Generic type 'C<T>' requires 1 type argument(s).
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument.d.ts(11,26): error TS2314: Generic type 'C<T>' requires 1 type argument(s).
-tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument.d.ts(12,19): error TS1023: An index signature parameter type must be 'string', 'number', or 'symbol'.
+tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument.d.ts(12,19): error TS1023: An index signature parameter type must be 'string' or 'number'.
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument.d.ts(12,22): error TS2314: Generic type 'C<T>' requires 1 type argument(s).
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument.d.ts(12,26): error TS2314: Generic type 'C<T>' requires 1 type argument(s).
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument.d.ts(14,23): error TS2314: Generic type 'C<T>' requires 1 type argument(s).
@@ -36,7 +36,7 @@ tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenc
 !!! error TS2314: Generic type 'C<T>' requires 1 type argument(s).
     declare var d: { [x: C]: C };
                       ~
-!!! error TS1023: An index signature parameter type must be 'string', 'number', or 'symbol'.
+!!! error TS1023: An index signature parameter type must be 'string' or 'number'.
                          ~
 !!! error TS2314: Generic type 'C<T>' requires 1 type argument(s).
                              ~
diff --git a/tests/baselines/reference/genericTypeReferenceWithoutTypeArgument.errors.txt b/tests/baselines/reference/genericTypeReferenceWithoutTypeArgument.errors.txt
index 7b5116356c7..d57f3c2fc0d 100644
--- a/tests/baselines/reference/genericTypeReferenceWithoutTypeArgument.errors.txt
+++ b/tests/baselines/reference/genericTypeReferenceWithoutTypeArgument.errors.txt
@@ -2,7 +2,7 @@ tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenc
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument.ts(10,13): error TS2314: Generic type 'C<T>' requires 1 type argument(s).
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument.ts(11,14): error TS2314: Generic type 'C<T>' requires 1 type argument(s).
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument.ts(11,18): error TS2314: Generic type 'C<T>' requires 1 type argument(s).
-tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument.ts(12,11): error TS1023: An index signature parameter type must be 'string', 'number', or 'symbol'.
+tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument.ts(12,11): error TS1023: An index signature parameter type must be 'string' or 'number'.
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument.ts(12,14): error TS2314: Generic type 'C<T>' requires 1 type argument(s).
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument.ts(12,18): error TS2314: Generic type 'C<T>' requires 1 type argument(s).
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument.ts(14,13): error TS2314: Generic type 'C<T>' requires 1 type argument(s).
@@ -46,7 +46,7 @@ tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenc
 !!! error TS2314: Generic type 'C<T>' requires 1 type argument(s).
     var d: { [x: C]: C };
               ~
-!!! error TS1023: An index signature parameter type must be 'string', 'number', or 'symbol'.
+!!! error TS1023: An index signature parameter type must be 'string' or 'number'.
                  ~
 !!! error TS2314: Generic type 'C<T>' requires 1 type argument(s).
                      ~
diff --git a/tests/baselines/reference/genericTypeReferenceWithoutTypeArgument2.errors.txt b/tests/baselines/reference/genericTypeReferenceWithoutTypeArgument2.errors.txt
index 136682b1ca1..745da9aa106 100644
--- a/tests/baselines/reference/genericTypeReferenceWithoutTypeArgument2.errors.txt
+++ b/tests/baselines/reference/genericTypeReferenceWithoutTypeArgument2.errors.txt
@@ -2,7 +2,7 @@ tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenc
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument2.ts(10,13): error TS2314: Generic type 'I<T>' requires 1 type argument(s).
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument2.ts(11,14): error TS2314: Generic type 'I<T>' requires 1 type argument(s).
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument2.ts(11,18): error TS2314: Generic type 'I<T>' requires 1 type argument(s).
-tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument2.ts(12,11): error TS1023: An index signature parameter type must be 'string', 'number', or 'symbol'.
+tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument2.ts(12,11): error TS1023: An index signature parameter type must be 'string' or 'number'.
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument2.ts(12,14): error TS2314: Generic type 'I<T>' requires 1 type argument(s).
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument2.ts(12,18): error TS2314: Generic type 'I<T>' requires 1 type argument(s).
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument2.ts(14,13): error TS2314: Generic type 'I<T>' requires 1 type argument(s).
@@ -46,7 +46,7 @@ tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenc
 !!! error TS2314: Generic type 'I<T>' requires 1 type argument(s).
     var d: { [x: I]: I };
               ~
-!!! error TS1023: An index signature parameter type must be 'string', 'number', or 'symbol'.
+!!! error TS1023: An index signature parameter type must be 'string' or 'number'.
                  ~
 !!! error TS2314: Generic type 'I<T>' requires 1 type argument(s).
                      ~
diff --git a/tests/baselines/reference/genericTypeReferenceWithoutTypeArgument3.errors.txt b/tests/baselines/reference/genericTypeReferenceWithoutTypeArgument3.errors.txt
index d755a9120a8..1fec52356a2 100644
--- a/tests/baselines/reference/genericTypeReferenceWithoutTypeArgument3.errors.txt
+++ b/tests/baselines/reference/genericTypeReferenceWithoutTypeArgument3.errors.txt
@@ -2,7 +2,7 @@ tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenc
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument3.ts(10,21): error TS2314: Generic type 'C<T>' requires 1 type argument(s).
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument3.ts(11,22): error TS2314: Generic type 'C<T>' requires 1 type argument(s).
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument3.ts(11,26): error TS2314: Generic type 'C<T>' requires 1 type argument(s).
-tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument3.ts(12,19): error TS1023: An index signature parameter type must be 'string', 'number', or 'symbol'.
+tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument3.ts(12,19): error TS1023: An index signature parameter type must be 'string' or 'number'.
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument3.ts(12,22): error TS2314: Generic type 'C<T>' requires 1 type argument(s).
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument3.ts(12,26): error TS2314: Generic type 'C<T>' requires 1 type argument(s).
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument3.ts(14,23): error TS2314: Generic type 'C<T>' requires 1 type argument(s).
@@ -36,7 +36,7 @@ tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenc
 !!! error TS2314: Generic type 'C<T>' requires 1 type argument(s).
     declare var d: { [x: C]: C };
                       ~
-!!! error TS1023: An index signature parameter type must be 'string', 'number', or 'symbol'.
+!!! error TS1023: An index signature parameter type must be 'string' or 'number'.
                          ~
 !!! error TS2314: Generic type 'C<T>' requires 1 type argument(s).
                              ~
diff --git a/tests/baselines/reference/indexTypeCheck.errors.txt b/tests/baselines/reference/indexTypeCheck.errors.txt
index 5d3e6dc9268..9f4b403ca2e 100644
--- a/tests/baselines/reference/indexTypeCheck.errors.txt
+++ b/tests/baselines/reference/indexTypeCheck.errors.txt
@@ -4,7 +4,7 @@ tests/cases/compiler/indexTypeCheck.ts(17,2): error TS2413: Numeric index type '
 tests/cases/compiler/indexTypeCheck.ts(22,2): error TS2413: Numeric index type 'Orange' is not assignable to string index type 'Yellow'.
 tests/cases/compiler/indexTypeCheck.ts(27,2): error TS2413: Numeric index type 'number' is not assignable to string index type 'string'.
 tests/cases/compiler/indexTypeCheck.ts(32,3): error TS1096: An index signature must have exactly one parameter.
-tests/cases/compiler/indexTypeCheck.ts(36,3): error TS1023: An index signature parameter type must be 'string', 'number', or 'symbol'.
+tests/cases/compiler/indexTypeCheck.ts(36,3): error TS1023: An index signature parameter type must be 'string' or 'number'.
 tests/cases/compiler/indexTypeCheck.ts(51,1): error TS2342: An index expression argument must be of type 'string', 'number', 'symbol, or 'any'.
 
 
@@ -58,7 +58,7 @@ tests/cases/compiler/indexTypeCheck.ts(51,1): error TS2342: An index expression
     interface Magenta {
     	[p:Purple]; // error
     	 ~
-!!! error TS1023: An index signature parameter type must be 'string', 'number', or 'symbol'.
+!!! error TS1023: An index signature parameter type must be 'string' or 'number'.
     }
     
     var yellow: Yellow;
diff --git a/tests/baselines/reference/parserES5SymbolIndexer1.errors.txt b/tests/baselines/reference/parserES5SymbolIndexer1.errors.txt
index a3c4f22a87e..adfac8f700f 100644
--- a/tests/baselines/reference/parserES5SymbolIndexer1.errors.txt
+++ b/tests/baselines/reference/parserES5SymbolIndexer1.errors.txt
@@ -1,9 +1,9 @@
-tests/cases/conformance/parser/ecmascript5/Symbols/parserES5SymbolIndexer1.ts(2,9): error TS1188: 'symbol' indexers are only available when targeting ECMAScript 6 and higher.
+tests/cases/conformance/parser/ecmascript5/Symbols/parserES5SymbolIndexer1.ts(2,6): error TS1023: An index signature parameter type must be 'string' or 'number'.
 
 
 ==== tests/cases/conformance/parser/ecmascript5/Symbols/parserES5SymbolIndexer1.ts (1 errors) ====
     interface I {
         [s: symbol]: string;
-            ~~~~~~
-!!! error TS1188: 'symbol' indexers are only available when targeting ECMAScript 6 and higher.
+         ~
+!!! error TS1023: An index signature parameter type must be 'string' or 'number'.
     }
\ No newline at end of file
diff --git a/tests/baselines/reference/parserES5SymbolIndexer2.errors.txt b/tests/baselines/reference/parserES5SymbolIndexer2.errors.txt
index 39d8aa41d77..12eef8ec049 100644
--- a/tests/baselines/reference/parserES5SymbolIndexer2.errors.txt
+++ b/tests/baselines/reference/parserES5SymbolIndexer2.errors.txt
@@ -1,9 +1,9 @@
-tests/cases/conformance/parser/ecmascript5/Symbols/parserES5SymbolIndexer2.ts(2,9): error TS1188: 'symbol' indexers are only available when targeting ECMAScript 6 and higher.
+tests/cases/conformance/parser/ecmascript5/Symbols/parserES5SymbolIndexer2.ts(2,6): error TS1023: An index signature parameter type must be 'string' or 'number'.
 
 
 ==== tests/cases/conformance/parser/ecmascript5/Symbols/parserES5SymbolIndexer2.ts (1 errors) ====
     class C {
         [s: symbol]: string;
-            ~~~~~~
-!!! error TS1188: 'symbol' indexers are only available when targeting ECMAScript 6 and higher.
+         ~
+!!! error TS1023: An index signature parameter type must be 'string' or 'number'.
     }
\ No newline at end of file
diff --git a/tests/baselines/reference/parserES5SymbolIndexer3.errors.txt b/tests/baselines/reference/parserES5SymbolIndexer3.errors.txt
index 34dea325439..c9cd9db4fab 100644
--- a/tests/baselines/reference/parserES5SymbolIndexer3.errors.txt
+++ b/tests/baselines/reference/parserES5SymbolIndexer3.errors.txt
@@ -1,9 +1,9 @@
-tests/cases/conformance/parser/ecmascript5/Symbols/parserES5SymbolIndexer3.ts(2,9): error TS1188: 'symbol' indexers are only available when targeting ECMAScript 6 and higher.
+tests/cases/conformance/parser/ecmascript5/Symbols/parserES5SymbolIndexer3.ts(2,6): error TS1023: An index signature parameter type must be 'string' or 'number'.
 
 
 ==== tests/cases/conformance/parser/ecmascript5/Symbols/parserES5SymbolIndexer3.ts (1 errors) ====
     var x: {
         [s: symbol]: string;
-            ~~~~~~
-!!! error TS1188: 'symbol' indexers are only available when targeting ECMAScript 6 and higher.
+         ~
+!!! error TS1023: An index signature parameter type must be 'string' or 'number'.
     }
\ No newline at end of file
diff --git a/tests/baselines/reference/parserIndexSignature6.errors.txt b/tests/baselines/reference/parserIndexSignature6.errors.txt
index 52a3b28a519..db53f219832 100644
--- a/tests/baselines/reference/parserIndexSignature6.errors.txt
+++ b/tests/baselines/reference/parserIndexSignature6.errors.txt
@@ -1,9 +1,9 @@
-tests/cases/conformance/parser/ecmascript5/IndexSignatures/parserIndexSignature6.ts(2,4): error TS1023: An index signature parameter type must be 'string', 'number', or 'symbol'.
+tests/cases/conformance/parser/ecmascript5/IndexSignatures/parserIndexSignature6.ts(2,4): error TS1023: An index signature parameter type must be 'string' or 'number'.
 
 
 ==== tests/cases/conformance/parser/ecmascript5/IndexSignatures/parserIndexSignature6.ts (1 errors) ====
     interface I {
       [a:boolean]
        ~
-!!! error TS1023: An index signature parameter type must be 'string', 'number', or 'symbol'.
+!!! error TS1023: An index signature parameter type must be 'string' or 'number'.
     }
\ No newline at end of file
diff --git a/tests/baselines/reference/parserIndexSignature8.errors.txt b/tests/baselines/reference/parserIndexSignature8.errors.txt
index efed14e9577..87369df1b76 100644
--- a/tests/baselines/reference/parserIndexSignature8.errors.txt
+++ b/tests/baselines/reference/parserIndexSignature8.errors.txt
@@ -1,12 +1,12 @@
-tests/cases/conformance/parser/ecmascript5/IndexSignatures/parserIndexSignature8.ts(1,13): error TS1023: An index signature parameter type must be 'string', 'number', or 'symbol'.
-tests/cases/conformance/parser/ecmascript5/IndexSignatures/parserIndexSignature8.ts(2,14): error TS1023: An index signature parameter type must be 'string', 'number', or 'symbol'.
+tests/cases/conformance/parser/ecmascript5/IndexSignatures/parserIndexSignature8.ts(1,13): error TS1023: An index signature parameter type must be 'string' or 'number'.
+tests/cases/conformance/parser/ecmascript5/IndexSignatures/parserIndexSignature8.ts(2,14): error TS1023: An index signature parameter type must be 'string' or 'number'.
 
 
 ==== tests/cases/conformance/parser/ecmascript5/IndexSignatures/parserIndexSignature8.ts (2 errors) ====
     var foo: { [index: any]; }; // expect an error here
                 ~~~~~
-!!! error TS1023: An index signature parameter type must be 'string', 'number', or 'symbol'.
+!!! error TS1023: An index signature parameter type must be 'string' or 'number'.
     var foo2: { [index: RegExp]; }; // expect an error here
                  ~~~~~
-!!! error TS1023: An index signature parameter type must be 'string', 'number', or 'symbol'.
+!!! error TS1023: An index signature parameter type must be 'string' or 'number'.
     
\ No newline at end of file
diff --git a/tests/baselines/reference/parserSymbolIndexer1.errors.txt b/tests/baselines/reference/parserSymbolIndexer1.errors.txt
new file mode 100644
index 00000000000..5c6c38d52b1
--- /dev/null
+++ b/tests/baselines/reference/parserSymbolIndexer1.errors.txt
@@ -0,0 +1,9 @@
+tests/cases/conformance/parser/ecmascript6/Symbols/parserSymbolIndexer1.ts(2,6): error TS1023: An index signature parameter type must be 'string' or 'number'.
+
+
+==== tests/cases/conformance/parser/ecmascript6/Symbols/parserSymbolIndexer1.ts (1 errors) ====
+    interface I {
+        [s: symbol]: string;
+         ~
+!!! error TS1023: An index signature parameter type must be 'string' or 'number'.
+    }
\ No newline at end of file
diff --git a/tests/baselines/reference/parserSymbolIndexer1.types b/tests/baselines/reference/parserSymbolIndexer1.types
deleted file mode 100644
index 6723ef12726..00000000000
--- a/tests/baselines/reference/parserSymbolIndexer1.types
+++ /dev/null
@@ -1,7 +0,0 @@
-=== tests/cases/conformance/parser/ecmascript6/Symbols/parserSymbolIndexer1.ts ===
-interface I {
->I : I
-
-    [s: symbol]: string;
->s : symbol
-}
diff --git a/tests/baselines/reference/parserSymbolIndexer2.errors.txt b/tests/baselines/reference/parserSymbolIndexer2.errors.txt
new file mode 100644
index 00000000000..3961f4942de
--- /dev/null
+++ b/tests/baselines/reference/parserSymbolIndexer2.errors.txt
@@ -0,0 +1,9 @@
+tests/cases/conformance/parser/ecmascript6/Symbols/parserSymbolIndexer2.ts(2,6): error TS1023: An index signature parameter type must be 'string' or 'number'.
+
+
+==== tests/cases/conformance/parser/ecmascript6/Symbols/parserSymbolIndexer2.ts (1 errors) ====
+    class C {
+        [s: symbol]: string;
+         ~
+!!! error TS1023: An index signature parameter type must be 'string' or 'number'.
+    }
\ No newline at end of file
diff --git a/tests/baselines/reference/parserSymbolIndexer2.types b/tests/baselines/reference/parserSymbolIndexer2.types
deleted file mode 100644
index d8d620c7def..00000000000
--- a/tests/baselines/reference/parserSymbolIndexer2.types
+++ /dev/null
@@ -1,7 +0,0 @@
-=== tests/cases/conformance/parser/ecmascript6/Symbols/parserSymbolIndexer2.ts ===
-class C {
->C : C
-
-    [s: symbol]: string;
->s : symbol
-}
diff --git a/tests/baselines/reference/parserSymbolIndexer3.errors.txt b/tests/baselines/reference/parserSymbolIndexer3.errors.txt
index df3b9596f79..5484a096d4c 100644
--- a/tests/baselines/reference/parserSymbolIndexer3.errors.txt
+++ b/tests/baselines/reference/parserSymbolIndexer3.errors.txt
@@ -1,9 +1,9 @@
-tests/cases/conformance/parser/ecmascript6/Symbols/parserSymbolIndexer3.ts(2,5): error TS1145: Modifiers not permitted on index signature members.
+tests/cases/conformance/parser/ecmascript6/Symbols/parserSymbolIndexer3.ts(2,13): error TS1023: An index signature parameter type must be 'string' or 'number'.
 
 
 ==== tests/cases/conformance/parser/ecmascript6/Symbols/parserSymbolIndexer3.ts (1 errors) ====
     class C {
         static [s: symbol]: string;
-        ~~~~~~
-!!! error TS1145: Modifiers not permitted on index signature members.
+                ~
+!!! error TS1023: An index signature parameter type must be 'string' or 'number'.
     }
\ No newline at end of file
diff --git a/tests/baselines/reference/parserSymbolIndexer4.errors.txt b/tests/baselines/reference/parserSymbolIndexer4.errors.txt
new file mode 100644
index 00000000000..1cf184a4847
--- /dev/null
+++ b/tests/baselines/reference/parserSymbolIndexer4.errors.txt
@@ -0,0 +1,9 @@
+tests/cases/conformance/parser/ecmascript6/Symbols/parserSymbolIndexer4.ts(2,6): error TS1023: An index signature parameter type must be 'string' or 'number'.
+
+
+==== tests/cases/conformance/parser/ecmascript6/Symbols/parserSymbolIndexer4.ts (1 errors) ====
+    var x: {
+        [s: symbol]: string;
+         ~
+!!! error TS1023: An index signature parameter type must be 'string' or 'number'.
+    }
\ No newline at end of file
diff --git a/tests/baselines/reference/parserSymbolIndexer4.types b/tests/baselines/reference/parserSymbolIndexer4.types
deleted file mode 100644
index 7509072a12c..00000000000
--- a/tests/baselines/reference/parserSymbolIndexer4.types
+++ /dev/null
@@ -1,7 +0,0 @@
-=== tests/cases/conformance/parser/ecmascript6/Symbols/parserSymbolIndexer4.ts ===
-var x: {
->x : {}
-
-    [s: symbol]: string;
->s : symbol
-}
diff --git a/tests/baselines/reference/symbolProperty17.errors.txt b/tests/baselines/reference/symbolProperty17.errors.txt
new file mode 100644
index 00000000000..51f77646f0d
--- /dev/null
+++ b/tests/baselines/reference/symbolProperty17.errors.txt
@@ -0,0 +1,14 @@
+tests/cases/conformance/es6/Symbols/symbolProperty17.ts(3,6): error TS1023: An index signature parameter type must be 'string' or 'number'.
+
+
+==== tests/cases/conformance/es6/Symbols/symbolProperty17.ts (1 errors) ====
+    interface I {
+        [Symbol.iterator]: number;
+        [s: symbol]: string;
+         ~
+!!! error TS1023: An index signature parameter type must be 'string' or 'number'.
+        "__@iterator": string;
+    }
+    
+    var i: I;
+    var it = i[Symbol.iterator];
\ No newline at end of file
diff --git a/tests/baselines/reference/symbolProperty17.types b/tests/baselines/reference/symbolProperty17.types
deleted file mode 100644
index f804943c212..00000000000
--- a/tests/baselines/reference/symbolProperty17.types
+++ /dev/null
@@ -1,27 +0,0 @@
-=== tests/cases/conformance/es6/Symbols/symbolProperty17.ts ===
-interface I {
->I : I
-
-    [Symbol.iterator]: number;
->Symbol.iterator : symbol
->Symbol : SymbolConstructor
->iterator : symbol
-
-    [s: symbol]: string;
->s : symbol
-
-    "__@iterator": string;
-}
-
-var i: I;
->i : I
->I : I
-
-var it = i[Symbol.iterator];
->it : number
->i[Symbol.iterator] : number
->i : I
->Symbol.iterator : symbol
->Symbol : SymbolConstructor
->iterator : symbol
-
diff --git a/tests/baselines/reference/symbolProperty29.errors.txt b/tests/baselines/reference/symbolProperty29.errors.txt
new file mode 100644
index 00000000000..1efaeb2b3bf
--- /dev/null
+++ b/tests/baselines/reference/symbolProperty29.errors.txt
@@ -0,0 +1,12 @@
+tests/cases/conformance/es6/Symbols/symbolProperty29.ts(5,6): error TS1023: An index signature parameter type must be 'string' or 'number'.
+
+
+==== tests/cases/conformance/es6/Symbols/symbolProperty29.ts (1 errors) ====
+    class C1 {
+        [Symbol.toStringTag]() {
+            return { x: "" };
+        }
+        [s: symbol]: () => { x: string };
+         ~
+!!! error TS1023: An index signature parameter type must be 'string' or 'number'.
+    }
\ No newline at end of file
diff --git a/tests/baselines/reference/symbolProperty29.types b/tests/baselines/reference/symbolProperty29.types
deleted file mode 100644
index eb47ccae859..00000000000
--- a/tests/baselines/reference/symbolProperty29.types
+++ /dev/null
@@ -1,17 +0,0 @@
-=== tests/cases/conformance/es6/Symbols/symbolProperty29.ts ===
-class C1 {
->C1 : C1
-
-    [Symbol.toStringTag]() {
->Symbol.toStringTag : symbol
->Symbol : SymbolConstructor
->toStringTag : symbol
-
-        return { x: "" };
->{ x: "" } : { x: string; }
->x : string
-    }
-    [s: symbol]: () => { x: string };
->s : symbol
->x : string
-}
diff --git a/tests/baselines/reference/symbolProperty30.errors.txt b/tests/baselines/reference/symbolProperty30.errors.txt
new file mode 100644
index 00000000000..b839d11d1b8
--- /dev/null
+++ b/tests/baselines/reference/symbolProperty30.errors.txt
@@ -0,0 +1,12 @@
+tests/cases/conformance/es6/Symbols/symbolProperty30.ts(5,6): error TS1023: An index signature parameter type must be 'string' or 'number'.
+
+
+==== tests/cases/conformance/es6/Symbols/symbolProperty30.ts (1 errors) ====
+    class C1 {
+        [Symbol.toStringTag]() {
+            return { x: "" };
+        }
+        [s: symbol]: () => { x: number };
+         ~
+!!! error TS1023: An index signature parameter type must be 'string' or 'number'.
+    }
\ No newline at end of file
diff --git a/tests/baselines/reference/symbolProperty31.errors.txt b/tests/baselines/reference/symbolProperty31.errors.txt
new file mode 100644
index 00000000000..39735c017b2
--- /dev/null
+++ b/tests/baselines/reference/symbolProperty31.errors.txt
@@ -0,0 +1,14 @@
+tests/cases/conformance/es6/Symbols/symbolProperty31.ts(7,6): error TS1023: An index signature parameter type must be 'string' or 'number'.
+
+
+==== tests/cases/conformance/es6/Symbols/symbolProperty31.ts (1 errors) ====
+    class C1 {
+        [Symbol.toStringTag]() {
+            return { x: "" };
+        }
+    }
+    class C2 extends C1 {
+        [s: symbol]: () => { x: string };
+         ~
+!!! error TS1023: An index signature parameter type must be 'string' or 'number'.
+    }
\ No newline at end of file
diff --git a/tests/baselines/reference/symbolProperty31.types b/tests/baselines/reference/symbolProperty31.types
deleted file mode 100644
index 52a6523d4ed..00000000000
--- a/tests/baselines/reference/symbolProperty31.types
+++ /dev/null
@@ -1,22 +0,0 @@
-=== tests/cases/conformance/es6/Symbols/symbolProperty31.ts ===
-class C1 {
->C1 : C1
-
-    [Symbol.toStringTag]() {
->Symbol.toStringTag : symbol
->Symbol : SymbolConstructor
->toStringTag : symbol
-
-        return { x: "" };
->{ x: "" } : { x: string; }
->x : string
-    }
-}
-class C2 extends C1 {
->C2 : C2
->C1 : C1
-
-    [s: symbol]: () => { x: string };
->s : symbol
->x : string
-}
diff --git a/tests/baselines/reference/symbolProperty32.errors.txt b/tests/baselines/reference/symbolProperty32.errors.txt
new file mode 100644
index 00000000000..4051f8f91c8
--- /dev/null
+++ b/tests/baselines/reference/symbolProperty32.errors.txt
@@ -0,0 +1,14 @@
+tests/cases/conformance/es6/Symbols/symbolProperty32.ts(7,6): error TS1023: An index signature parameter type must be 'string' or 'number'.
+
+
+==== tests/cases/conformance/es6/Symbols/symbolProperty32.ts (1 errors) ====
+    class C1 {
+        [Symbol.toStringTag]() {
+            return { x: "" };
+        }
+    }
+    class C2 extends C1 {
+        [s: symbol]: () => { x: number };
+         ~
+!!! error TS1023: An index signature parameter type must be 'string' or 'number'.
+    }
\ No newline at end of file
diff --git a/tests/baselines/reference/symbolProperty33.errors.txt b/tests/baselines/reference/symbolProperty33.errors.txt
new file mode 100644
index 00000000000..25a16b045ab
--- /dev/null
+++ b/tests/baselines/reference/symbolProperty33.errors.txt
@@ -0,0 +1,14 @@
+tests/cases/conformance/es6/Symbols/symbolProperty33.ts(7,6): error TS1023: An index signature parameter type must be 'string' or 'number'.
+
+
+==== tests/cases/conformance/es6/Symbols/symbolProperty33.ts (1 errors) ====
+    class C1 extends C2 {
+        [Symbol.toStringTag]() {
+            return { x: "" };
+        }
+    }
+    class C2 {
+        [s: symbol]: () => { x: string };
+         ~
+!!! error TS1023: An index signature parameter type must be 'string' or 'number'.
+    }
\ No newline at end of file
diff --git a/tests/baselines/reference/symbolProperty33.types b/tests/baselines/reference/symbolProperty33.types
deleted file mode 100644
index aed8a97e60b..00000000000
--- a/tests/baselines/reference/symbolProperty33.types
+++ /dev/null
@@ -1,22 +0,0 @@
-=== tests/cases/conformance/es6/Symbols/symbolProperty33.ts ===
-class C1 extends C2 {
->C1 : C1
->C2 : C2
-
-    [Symbol.toStringTag]() {
->Symbol.toStringTag : symbol
->Symbol : SymbolConstructor
->toStringTag : symbol
-
-        return { x: "" };
->{ x: "" } : { x: string; }
->x : string
-    }
-}
-class C2 {
->C2 : C2
-
-    [s: symbol]: () => { x: string };
->s : symbol
->x : string
-}
diff --git a/tests/baselines/reference/symbolProperty34.errors.txt b/tests/baselines/reference/symbolProperty34.errors.txt
new file mode 100644
index 00000000000..4339af94788
--- /dev/null
+++ b/tests/baselines/reference/symbolProperty34.errors.txt
@@ -0,0 +1,14 @@
+tests/cases/conformance/es6/Symbols/symbolProperty34.ts(7,6): error TS1023: An index signature parameter type must be 'string' or 'number'.
+
+
+==== tests/cases/conformance/es6/Symbols/symbolProperty34.ts (1 errors) ====
+    class C1 extends C2 {
+        [Symbol.toStringTag]() {
+            return { x: "" };
+        }
+    }
+    class C2 {
+        [s: symbol]: () => { x: number };
+         ~
+!!! error TS1023: An index signature parameter type must be 'string' or 'number'.
+    }
\ No newline at end of file