diff --git a/src/compiler/program.ts b/src/compiler/program.ts
index 39a55afe27a13..d70d1f8f60d9e 100644
--- a/src/compiler/program.ts
+++ b/src/compiler/program.ts
@@ -2263,7 +2263,7 @@ namespace ts {
             const languageVersion = options.target || ScriptTarget.ES3;
             const outFile = options.outFile || options.out;
 
-            const firstExternalModuleSourceFile = forEach(files, f => isExternalModule(f) ? f : undefined);
+            const firstNonAmbientExternalModuleSourceFile = forEach(files, f => isExternalModule(f) && !isDeclarationFile(f) ? f : undefined);
             if (options.isolatedModules) {
                 if (options.module === ModuleKind.None && languageVersion < ScriptTarget.ES6) {
                     programDiagnostics.add(createCompilerDiagnostic(Diagnostics.Option_isolatedModules_can_only_be_used_when_either_option_module_is_provided_or_option_target_is_ES2015_or_higher));
@@ -2275,10 +2275,10 @@ namespace ts {
                     programDiagnostics.add(createFileDiagnostic(firstNonExternalModuleSourceFile, span.start, span.length, Diagnostics.Cannot_compile_namespaces_when_the_isolatedModules_flag_is_provided));
                 }
             }
-            else if (firstExternalModuleSourceFile && languageVersion < ScriptTarget.ES6 && options.module === ModuleKind.None) {
+            else if (firstNonAmbientExternalModuleSourceFile && languageVersion < ScriptTarget.ES6 && options.module === ModuleKind.None) {
                 // We cannot use createDiagnosticFromNode because nodes do not have parents yet
-                const span = getErrorSpanForNode(firstExternalModuleSourceFile, firstExternalModuleSourceFile.externalModuleIndicator);
-                programDiagnostics.add(createFileDiagnostic(firstExternalModuleSourceFile, span.start, span.length, Diagnostics.Cannot_use_imports_exports_or_module_augmentations_when_module_is_none));
+                const span = getErrorSpanForNode(firstNonAmbientExternalModuleSourceFile, firstNonAmbientExternalModuleSourceFile.externalModuleIndicator);
+                programDiagnostics.add(createFileDiagnostic(firstNonAmbientExternalModuleSourceFile, span.start, span.length, Diagnostics.Cannot_use_imports_exports_or_module_augmentations_when_module_is_none));
             }
 
             // Cannot specify module gen that isn't amd or system with --out
@@ -2286,9 +2286,9 @@ namespace ts {
                 if (options.module && !(options.module === ModuleKind.AMD || options.module === ModuleKind.System)) {
                     programDiagnostics.add(createCompilerDiagnostic(Diagnostics.Only_amd_and_system_modules_are_supported_alongside_0, options.out ? "out" : "outFile"));
                 }
-                else if (options.module === undefined && firstExternalModuleSourceFile) {
-                    const span = getErrorSpanForNode(firstExternalModuleSourceFile, firstExternalModuleSourceFile.externalModuleIndicator);
-                    programDiagnostics.add(createFileDiagnostic(firstExternalModuleSourceFile, span.start, span.length, Diagnostics.Cannot_compile_modules_using_option_0_unless_the_module_flag_is_amd_or_system, options.out ? "out" : "outFile"));
+                else if (options.module === undefined && firstNonAmbientExternalModuleSourceFile) {
+                    const span = getErrorSpanForNode(firstNonAmbientExternalModuleSourceFile, firstNonAmbientExternalModuleSourceFile.externalModuleIndicator);
+                    programDiagnostics.add(createFileDiagnostic(firstNonAmbientExternalModuleSourceFile, span.start, span.length, Diagnostics.Cannot_compile_modules_using_option_0_unless_the_module_flag_is_amd_or_system, options.out ? "out" : "outFile"));
                 }
             }
 
diff --git a/tests/baselines/reference/noErrorUsingImportExportModuleAugmentationInDeclarationFile1.symbols b/tests/baselines/reference/noErrorUsingImportExportModuleAugmentationInDeclarationFile1.symbols
new file mode 100644
index 0000000000000..d3d338e0d14d7
--- /dev/null
+++ b/tests/baselines/reference/noErrorUsingImportExportModuleAugmentationInDeclarationFile1.symbols
@@ -0,0 +1,8 @@
+=== tests/cases/compiler/0.d.ts ===
+
+export = a;
+>a : Symbol(a, Decl(0.d.ts, 2, 11))
+
+declare var a: number;
+>a : Symbol(a, Decl(0.d.ts, 2, 11))
+
diff --git a/tests/baselines/reference/noErrorUsingImportExportModuleAugmentationInDeclarationFile1.types b/tests/baselines/reference/noErrorUsingImportExportModuleAugmentationInDeclarationFile1.types
new file mode 100644
index 0000000000000..c5e2c0b80f889
--- /dev/null
+++ b/tests/baselines/reference/noErrorUsingImportExportModuleAugmentationInDeclarationFile1.types
@@ -0,0 +1,8 @@
+=== tests/cases/compiler/0.d.ts ===
+
+export = a;
+>a : number
+
+declare var a: number;
+>a : number
+
diff --git a/tests/baselines/reference/noErrorUsingImportExportModuleAugmentationInDeclarationFile2.errors.txt b/tests/baselines/reference/noErrorUsingImportExportModuleAugmentationInDeclarationFile2.errors.txt
new file mode 100644
index 0000000000000..bcf5d91c01510
--- /dev/null
+++ b/tests/baselines/reference/noErrorUsingImportExportModuleAugmentationInDeclarationFile2.errors.txt
@@ -0,0 +1,12 @@
+tests/cases/compiler/1.ts(2,1): error TS1148: Cannot use imports, exports, or module augmentations when '--module' is 'none'.
+
+
+==== tests/cases/compiler/1.ts (1 errors) ====
+    
+    export var j = "hello"; // error
+    ~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS1148: Cannot use imports, exports, or module augmentations when '--module' is 'none'.
+    
+==== tests/cases/compiler/0.d.ts (0 errors) ====
+    export = a;
+    declare var a: number;
\ No newline at end of file
diff --git a/tests/baselines/reference/noErrorUsingImportExportModuleAugmentationInDeclarationFile2.js b/tests/baselines/reference/noErrorUsingImportExportModuleAugmentationInDeclarationFile2.js
new file mode 100644
index 0000000000000..b56988de44cbb
--- /dev/null
+++ b/tests/baselines/reference/noErrorUsingImportExportModuleAugmentationInDeclarationFile2.js
@@ -0,0 +1,13 @@
+//// [tests/cases/compiler/noErrorUsingImportExportModuleAugmentationInDeclarationFile2.ts] ////
+
+//// [1.ts]
+
+export var j = "hello"; // error
+
+//// [0.d.ts]
+export = a;
+declare var a: number;
+
+//// [1.js]
+"use strict";
+exports.j = "hello"; // error
diff --git a/tests/baselines/reference/noErrorUsingImportExportModuleAugmentationInDeclarationFile3.errors.txt b/tests/baselines/reference/noErrorUsingImportExportModuleAugmentationInDeclarationFile3.errors.txt
new file mode 100644
index 0000000000000..eb215693cd756
--- /dev/null
+++ b/tests/baselines/reference/noErrorUsingImportExportModuleAugmentationInDeclarationFile3.errors.txt
@@ -0,0 +1,13 @@
+tests/cases/compiler/1.ts(1,1): error TS1148: Cannot use imports, exports, or module augmentations when '--module' is 'none'.
+
+
+==== tests/cases/compiler/0.d.ts (0 errors) ====
+    
+    export = a;
+    declare var a: number;
+    
+==== tests/cases/compiler/1.ts (1 errors) ====
+    export var j = "hello";  // error
+    ~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS1148: Cannot use imports, exports, or module augmentations when '--module' is 'none'.
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/noErrorUsingImportExportModuleAugmentationInDeclarationFile3.js b/tests/baselines/reference/noErrorUsingImportExportModuleAugmentationInDeclarationFile3.js
new file mode 100644
index 0000000000000..8c75af240346e
--- /dev/null
+++ b/tests/baselines/reference/noErrorUsingImportExportModuleAugmentationInDeclarationFile3.js
@@ -0,0 +1,14 @@
+//// [tests/cases/compiler/noErrorUsingImportExportModuleAugmentationInDeclarationFile3.ts] ////
+
+//// [0.d.ts]
+
+export = a;
+declare var a: number;
+
+//// [1.ts]
+export var j = "hello";  // error
+
+
+//// [1.js]
+"use strict";
+exports.j = "hello"; // error
diff --git a/tests/cases/compiler/noErrorUsingImportExportModuleAugmentationInDeclarationFile1.ts b/tests/cases/compiler/noErrorUsingImportExportModuleAugmentationInDeclarationFile1.ts
new file mode 100644
index 0000000000000..71ec411a4f5ce
--- /dev/null
+++ b/tests/cases/compiler/noErrorUsingImportExportModuleAugmentationInDeclarationFile1.ts
@@ -0,0 +1,5 @@
+// @module: none
+// @filename: 0.d.ts
+
+export = a;
+declare var a: number;
\ No newline at end of file
diff --git a/tests/cases/compiler/noErrorUsingImportExportModuleAugmentationInDeclarationFile2.ts b/tests/cases/compiler/noErrorUsingImportExportModuleAugmentationInDeclarationFile2.ts
new file mode 100644
index 0000000000000..160f80dba972c
--- /dev/null
+++ b/tests/cases/compiler/noErrorUsingImportExportModuleAugmentationInDeclarationFile2.ts
@@ -0,0 +1,8 @@
+// @module: none
+
+// @filename: 1.ts
+export var j = "hello"; // error
+
+// @filename: 0.d.ts
+export = a;
+declare var a: number;
\ No newline at end of file
diff --git a/tests/cases/compiler/noErrorUsingImportExportModuleAugmentationInDeclarationFile3.ts b/tests/cases/compiler/noErrorUsingImportExportModuleAugmentationInDeclarationFile3.ts
new file mode 100644
index 0000000000000..e13933a13d0a4
--- /dev/null
+++ b/tests/cases/compiler/noErrorUsingImportExportModuleAugmentationInDeclarationFile3.ts
@@ -0,0 +1,8 @@
+// @module: none
+
+// @filename: 0.d.ts
+export = a;
+declare var a: number;
+
+// @filename: 1.ts
+export var j = "hello";  // error