diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index a280be5f22f..8a17ff77f24 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -404,7 +404,7 @@ namespace ts {
                     mergeSymbol(mainModule, moduleAugmentation.symbol);
                 }
                 else {
-                    error(moduleName, Diagnostics.Cannot_augment_module_0_that_resolves_to_a_non_module_entity, moduleName.text);
+                    error(moduleName, Diagnostics.Cannot_augment_module_0_because_it_resolves_to_a_non_module_entity, moduleName.text);
                 }
             }
         }
diff --git a/src/compiler/diagnosticMessages.json b/src/compiler/diagnosticMessages.json
index 082077de01b..cb333e9036b 100644
--- a/src/compiler/diagnosticMessages.json
+++ b/src/compiler/diagnosticMessages.json
@@ -1819,7 +1819,7 @@
         "category": "Error",
         "code": 2670
     },
-    "Cannot augment module '{0}' that resolves to a non-module entity.": {
+    "Cannot augment module '{0}' because it resolves to a non-module entity.": {
         "category": "Error",
         "code": 2671
     },
diff --git a/tests/baselines/reference/augmentExportEquals1.errors.txt b/tests/baselines/reference/augmentExportEquals1.errors.txt
index ca3cc82cce8..2d15e6d622a 100644
--- a/tests/baselines/reference/augmentExportEquals1.errors.txt
+++ b/tests/baselines/reference/augmentExportEquals1.errors.txt
@@ -1,4 +1,4 @@
-tests/cases/compiler/file2.ts(6,16): error TS2671: Cannot augment module './file1' that resolves to a non-module entity.
+tests/cases/compiler/file2.ts(6,16): error TS2671: Cannot augment module './file1' because it resolves to a non-module entity.
 tests/cases/compiler/file3.ts(3,8): error TS2503: Cannot find namespace 'x'.
 
 
@@ -20,7 +20,7 @@ tests/cases/compiler/file3.ts(3,8): error TS2503: Cannot find namespace 'x'.
     // should error since './file1' does not have namespace meaning
     declare module "./file1" {
                    ~~~~~~~~~
-!!! error TS2671: Cannot augment module './file1' that resolves to a non-module entity.
+!!! error TS2671: Cannot augment module './file1' because it resolves to a non-module entity.
         interface A { a }
     }
     
\ No newline at end of file
diff --git a/tests/baselines/reference/augmentExportEquals1_1.errors.txt b/tests/baselines/reference/augmentExportEquals1_1.errors.txt
index 013bffc4504..aa89aa0c1d3 100644
--- a/tests/baselines/reference/augmentExportEquals1_1.errors.txt
+++ b/tests/baselines/reference/augmentExportEquals1_1.errors.txt
@@ -1,4 +1,4 @@
-tests/cases/compiler/file2.ts(6,16): error TS2671: Cannot augment module 'file1' that resolves to a non-module entity.
+tests/cases/compiler/file2.ts(6,16): error TS2671: Cannot augment module 'file1' because it resolves to a non-module entity.
 tests/cases/compiler/file3.ts(3,8): error TS2503: Cannot find namespace 'x'.
 
 
@@ -23,7 +23,7 @@ tests/cases/compiler/file3.ts(3,8): error TS2503: Cannot find namespace 'x'.
     // should error since 'file1' does not have namespace meaning
     declare module "file1" {
                    ~~~~~~~
-!!! error TS2671: Cannot augment module 'file1' that resolves to a non-module entity.
+!!! error TS2671: Cannot augment module 'file1' because it resolves to a non-module entity.
         interface A { a }
     }
     
\ No newline at end of file
diff --git a/tests/baselines/reference/augmentExportEquals2.errors.txt b/tests/baselines/reference/augmentExportEquals2.errors.txt
index 89c0778a3c9..b078a6623d7 100644
--- a/tests/baselines/reference/augmentExportEquals2.errors.txt
+++ b/tests/baselines/reference/augmentExportEquals2.errors.txt
@@ -1,4 +1,4 @@
-tests/cases/compiler/file2.ts(4,16): error TS2671: Cannot augment module './file1' that resolves to a non-module entity.
+tests/cases/compiler/file2.ts(4,16): error TS2671: Cannot augment module './file1' because it resolves to a non-module entity.
 tests/cases/compiler/file3.ts(3,8): error TS2503: Cannot find namespace 'x'.
 
 
@@ -19,7 +19,7 @@ tests/cases/compiler/file3.ts(3,8): error TS2503: Cannot find namespace 'x'.
     // should error since './file1' does not have namespace meaning
     declare module "./file1" {
                    ~~~~~~~~~
-!!! error TS2671: Cannot augment module './file1' that resolves to a non-module entity.
+!!! error TS2671: Cannot augment module './file1' because it resolves to a non-module entity.
         interface A { a }
     }
     
\ No newline at end of file
diff --git a/tests/baselines/reference/augmentExportEquals2_1.errors.txt b/tests/baselines/reference/augmentExportEquals2_1.errors.txt
index f0f571af5c4..8e02f21176a 100644
--- a/tests/baselines/reference/augmentExportEquals2_1.errors.txt
+++ b/tests/baselines/reference/augmentExportEquals2_1.errors.txt
@@ -1,4 +1,4 @@
-tests/cases/compiler/file2.ts(6,16): error TS2671: Cannot augment module 'file1' that resolves to a non-module entity.
+tests/cases/compiler/file2.ts(6,16): error TS2671: Cannot augment module 'file1' because it resolves to a non-module entity.
 tests/cases/compiler/file3.ts(3,8): error TS2503: Cannot find namespace 'x'.
 
 
@@ -23,7 +23,7 @@ tests/cases/compiler/file3.ts(3,8): error TS2503: Cannot find namespace 'x'.
     // should error since './file1' does not have namespace meaning
     declare module "file1" {
                    ~~~~~~~
-!!! error TS2671: Cannot augment module 'file1' that resolves to a non-module entity.
+!!! error TS2671: Cannot augment module 'file1' because it resolves to a non-module entity.
         interface A { a }
     }
     
\ No newline at end of file