diff --git a/src/compiler/diagnosticInformationMap.generated.ts b/src/compiler/diagnosticInformationMap.generated.ts
index cf30e250d85..7d1d63e5a56 100644
--- a/src/compiler/diagnosticInformationMap.generated.ts
+++ b/src/compiler/diagnosticInformationMap.generated.ts
@@ -431,6 +431,7 @@ namespace ts {
         Non_abstract_class_expression_does_not_implement_inherited_abstract_member_0_from_class_1: { code: 2653, category: DiagnosticCategory.Error, key: "Non-abstract class expression does not implement inherited abstract member '{0}' from class '{1}'." },
         Exported_external_package_typings_file_cannot_contain_tripleslash_references_Please_contact_the_package_author_to_update_the_package_definition: { code: 2654, category: DiagnosticCategory.Error, key: "Exported external package typings file cannot contain tripleslash references. Please contact the package author to update the package definition." },
         Exported_external_package_typings_can_only_be_in_d_ts_files_Please_contact_the_package_author_to_update_the_package_definition: { code: 2655, category: DiagnosticCategory.Error, key: "Exported external package typings can only be in '.d.ts' files. Please contact the package author to update the package definition." },
+        Exported_external_package_typings_file_0_is_not_a_module_Please_contact_the_package_author_to_update_the_package_definition: { code: 2656, category: DiagnosticCategory.Error, key: "Exported external package typings file '{0}' is not a module. Please contact the package author to update the package definition." },
         Import_declaration_0_is_using_private_name_1: { code: 4000, category: DiagnosticCategory.Error, key: "Import declaration '{0}' is using private name '{1}'." },
         Type_parameter_0_of_exported_class_has_or_is_using_private_name_1: { code: 4002, category: DiagnosticCategory.Error, key: "Type parameter '{0}' of exported class has or is using private name '{1}'." },
         Type_parameter_0_of_exported_interface_has_or_is_using_private_name_1: { code: 4004, category: DiagnosticCategory.Error, key: "Type parameter '{0}' of exported interface has or is using private name '{1}'." },
diff --git a/src/compiler/diagnosticMessages.json b/src/compiler/diagnosticMessages.json
index 4720303df25..245be4a3c9b 100644
--- a/src/compiler/diagnosticMessages.json
+++ b/src/compiler/diagnosticMessages.json
@@ -1713,6 +1713,10 @@
         "category": "Error",
         "code": 2655
     },
+    "Exported external package typings file '{0}' is not a module. Please contact the package author to update the package definition.": {
+        "category": "Error",
+        "code": 2656
+    },
     "Import declaration '{0}' is using private name '{1}'.": {
         "category": "Error",
         "code": 4000
diff --git a/src/compiler/program.ts b/src/compiler/program.ts
index 28dd477666b..1ac4151e834 100644
--- a/src/compiler/program.ts
+++ b/src/compiler/program.ts
@@ -863,7 +863,7 @@ namespace ts {
                         if (importedFile && resolution.isExternalLibraryImport) {
                             if (!isExternalModule(importedFile)) {
                                 let start = getTokenPosOfNode(file.imports[i], file)
-                                fileProcessingDiagnostics.add(createFileDiagnostic(file, start, file.imports[i].end - start, Diagnostics.File_0_is_not_a_module, importedFile.fileName));
+                                fileProcessingDiagnostics.add(createFileDiagnostic(file, start, file.imports[i].end - start, Diagnostics.Exported_external_package_typings_file_0_is_not_a_module_Please_contact_the_package_author_to_update_the_package_definition, importedFile.fileName));
                             }
                             else if (!fileExtensionIs(importedFile.fileName, ".d.ts")) {
                                 let start = getTokenPosOfNode(file.imports[i], file)
diff --git a/tests/baselines/reference/nodeResolution5.errors.txt b/tests/baselines/reference/nodeResolution5.errors.txt
index 1fc4e1cee52..c36cce45b6d 100644
--- a/tests/baselines/reference/nodeResolution5.errors.txt
+++ b/tests/baselines/reference/nodeResolution5.errors.txt
@@ -1,10 +1,10 @@
-tests/cases/compiler/b.ts(1,20): error TS2306: File 'tests/cases/compiler/node_modules/a.d.ts' is not a module.
+tests/cases/compiler/b.ts(1,20): error TS2656: Exported external package typings file 'tests/cases/compiler/node_modules/a.d.ts' is not a module. Please contact the package author to update the package definition.
 
 
 ==== tests/cases/compiler/b.ts (1 errors) ====
     import y = require("a"); 
                        ~~~
-!!! error TS2306: File 'a.d.ts' is not a module.
+!!! error TS2656: Exported external package typings file 'a.d.ts' is not a module. Please contact the package author to update the package definition.
     
 ==== tests/cases/compiler/node_modules/a.d.ts (0 errors) ====
     
diff --git a/tests/baselines/reference/nodeResolution7.errors.txt b/tests/baselines/reference/nodeResolution7.errors.txt
index 1e1f822f0d4..f9e8ef7ac0f 100644
--- a/tests/baselines/reference/nodeResolution7.errors.txt
+++ b/tests/baselines/reference/nodeResolution7.errors.txt
@@ -1,10 +1,10 @@
-tests/cases/compiler/b.ts(1,20): error TS2306: File 'tests/cases/compiler/node_modules/a/index.d.ts' is not a module.
+tests/cases/compiler/b.ts(1,20): error TS2656: Exported external package typings file 'tests/cases/compiler/node_modules/a/index.d.ts' is not a module. Please contact the package author to update the package definition.
 
 
 ==== tests/cases/compiler/b.ts (1 errors) ====
     import y = require("a"); 
                        ~~~
-!!! error TS2306: File 'index.d.ts' is not a module.
+!!! error TS2656: Exported external package typings file 'index.d.ts' is not a module. Please contact the package author to update the package definition.
     
 ==== tests/cases/compiler/node_modules/a/index.d.ts (0 errors) ====