diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index d4376becd6a..8983725d206 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -9947,7 +9947,20 @@ module ts {
                         break;
 
                     case SyntaxKind.DeclareKeyword:
-                        // TODO (yuisu) : Revisit this once moving ambient Context into type checking
+                        if (flags & NodeFlags.Ambient) {
+                            return grammarErrorOnNode(modifier, Diagnostics._0_modifier_already_seen, "declare");
+                        }
+                        else if (node.parent.kind === SyntaxKind.ClassDeclaration) {
+                            return grammarErrorOnNode(modifier, Diagnostics._0_modifier_cannot_appear_on_a_class_element, "declare");
+                        }
+                        else if (node.kind === SyntaxKind.Parameter) {
+                            return grammarErrorOnNode(modifier, Diagnostics._0_modifier_cannot_appear_on_a_parameter, "declare");
+                        }
+                        else if (isInAmbientContext(node.parent) && node.parent.kind === SyntaxKind.ModuleBlock) {
+                            return grammarErrorOnNode(modifier, Diagnostics.A_declare_modifier_cannot_be_used_in_an_already_ambient_context);
+                        }
+                        flags |= NodeFlags.Ambient;
+                        lastDeclare = modifier
                         break;
                 }
             }
diff --git a/src/compiler/diagnosticInformationMap.generated.ts b/src/compiler/diagnosticInformationMap.generated.ts
index 2050bad5ca5..fa21ddd03d4 100644
--- a/src/compiler/diagnosticInformationMap.generated.ts
+++ b/src/compiler/diagnosticInformationMap.generated.ts
@@ -33,7 +33,7 @@ module ts {
         Only_ambient_modules_can_use_quoted_names: { code: 1035, category: DiagnosticCategory.Error, key: "Only ambient modules can use quoted names.", isEarly: true },
         Statements_are_not_allowed_in_ambient_contexts: { code: 1036, category: DiagnosticCategory.Error, key: "Statements are not allowed in ambient contexts.", isEarly: true },
         A_function_implementation_cannot_be_declared_in_an_ambient_context: { code: 1037, category: DiagnosticCategory.Error, key: "A function implementation cannot be declared in an ambient context.", isEarly: true },
-        A_declare_modifier_cannot_be_used_in_an_already_ambient_context: { code: 1038, category: DiagnosticCategory.Error, key: "A 'declare' modifier cannot be used in an already ambient context." },
+        A_declare_modifier_cannot_be_used_in_an_already_ambient_context: { code: 1038, category: DiagnosticCategory.Error, key: "A 'declare' modifier cannot be used in an already ambient context.", isEarly: true },
         Initializers_are_not_allowed_in_ambient_contexts: { code: 1039, category: DiagnosticCategory.Error, key: "Initializers are not allowed in ambient contexts.", isEarly: true },
         _0_modifier_cannot_appear_on_a_module_element: { code: 1044, category: DiagnosticCategory.Error, key: "'{0}' modifier cannot appear on a module element.", isEarly: true },
         A_declare_modifier_cannot_be_used_with_an_interface_declaration: { code: 1045, category: DiagnosticCategory.Error, key: "A 'declare' modifier cannot be used with an interface declaration." },
diff --git a/src/compiler/diagnosticMessages.json b/src/compiler/diagnosticMessages.json
index 2cef9250a8f..3ddd6cf2a84 100644
--- a/src/compiler/diagnosticMessages.json
+++ b/src/compiler/diagnosticMessages.json
@@ -144,7 +144,8 @@
     },
     "A 'declare' modifier cannot be used in an already ambient context.": {
         "category": "Error",
-        "code": 1038
+        "code": 1038,
+        "isEarly":  true
     },
     "Initializers are not allowed in ambient contexts.": {
         "category": "Error",