diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index dfe6317e25072..f24d5e3e0cbfa 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -922,7 +922,7 @@ namespace ts {
                 if (result && isInExternalModule && (meaning & SymbolFlags.Value) === SymbolFlags.Value) {
                     const decls = result.declarations;
                     if (decls && decls.length === 1 && decls[0].kind === SyntaxKind.NamespaceExportDeclaration) {
-                        error(errorLocation, Diagnostics.Identifier_0_must_be_imported_from_a_module, name);
+                        error(errorLocation, Diagnostics._0_refers_to_a_UMD_global_but_the_current_file_is_a_module_Consider_adding_an_import_instead, name);
                     }
                 }
             }
diff --git a/src/compiler/diagnosticMessages.json b/src/compiler/diagnosticMessages.json
index 58c0e6ee3f21e..b99a1a91b8ea6 100644
--- a/src/compiler/diagnosticMessages.json
+++ b/src/compiler/diagnosticMessages.json
@@ -1923,7 +1923,7 @@
         "category": "Error",
         "code": 2685
     },
-    "Identifier '{0}' must be imported from a module": {
+    "'{0}' refers to a UMD global, but the current file is a module. Consider adding an import instead.": {
         "category": "Error",
         "code": 2686
     },
diff --git a/tests/baselines/reference/umd5.errors.txt b/tests/baselines/reference/umd5.errors.txt
index 9628ad738db86..5595de8de29fb 100644
--- a/tests/baselines/reference/umd5.errors.txt
+++ b/tests/baselines/reference/umd5.errors.txt
@@ -1,4 +1,4 @@
-tests/cases/conformance/externalModules/a.ts(6,9): error TS2686: Identifier 'Foo' must be imported from a module
+tests/cases/conformance/externalModules/a.ts(6,9): error TS2686: 'Foo' refers to a UMD global, but the current file is a module. Consider adding an import instead.
 
 
 ==== tests/cases/conformance/externalModules/a.ts (1 errors) ====
@@ -9,7 +9,7 @@ tests/cases/conformance/externalModules/a.ts(6,9): error TS2686: Identifier 'Foo
     // should error
     let z = Foo;
             ~~~
-!!! error TS2686: Identifier 'Foo' must be imported from a module
+!!! error TS2686: 'Foo' refers to a UMD global, but the current file is a module. Consider adding an import instead.
     
 ==== tests/cases/conformance/externalModules/foo.d.ts (0 errors) ====
     
diff --git a/tests/baselines/reference/umd8.errors.txt b/tests/baselines/reference/umd8.errors.txt
index 9396c8c5450bb..26c8adef56143 100644
--- a/tests/baselines/reference/umd8.errors.txt
+++ b/tests/baselines/reference/umd8.errors.txt
@@ -1,4 +1,4 @@
-tests/cases/conformance/externalModules/a.ts(7,14): error TS2686: Identifier 'Foo' must be imported from a module
+tests/cases/conformance/externalModules/a.ts(7,14): error TS2686: 'Foo' refers to a UMD global, but the current file is a module. Consider adding an import instead.
 
 
 ==== tests/cases/conformance/externalModules/a.ts (1 errors) ====
@@ -10,7 +10,7 @@ tests/cases/conformance/externalModules/a.ts(7,14): error TS2686: Identifier 'Fo
     let z: Foo.SubThing; // OK in ns position
     let x: any = Foo; // Not OK in value position
                  ~~~
-!!! error TS2686: Identifier 'Foo' must be imported from a module
+!!! error TS2686: 'Foo' refers to a UMD global, but the current file is a module. Consider adding an import instead.
     
 ==== tests/cases/conformance/externalModules/foo.d.ts (0 errors) ====