diff --git a/src/compiler/parser.ts b/src/compiler/parser.ts
index a1076464bbd..b0a9e02ed7c 100644
--- a/src/compiler/parser.ts
+++ b/src/compiler/parser.ts
@@ -537,7 +537,8 @@ namespace ts {
         }
 
         function getLanguageVariant(fileName: string) {
-            return isTsx(fileName) || isJavaScript(fileName) ?  LanguageVariant.JSX  : LanguageVariant.Standard;
+            // .tsx and .jsx files are treated as jsx language variant.
+            return fileExtensionIs(fileName, ".tsx") || fileExtensionIs(fileName, ".jsx") ?  LanguageVariant.JSX  : LanguageVariant.Standard;
         }
 
         function initializeState(fileName: string, _sourceText: string, languageVersion: ScriptTarget, _syntaxCursor: IncrementalParser.SyntaxCursor) {
diff --git a/src/compiler/utilities.ts b/src/compiler/utilities.ts
index 885d529f69e..838ff097933 100644
--- a/src/compiler/utilities.ts
+++ b/src/compiler/utilities.ts
@@ -2142,10 +2142,6 @@ namespace ts {
         return hasExtension(fileName) && forEach(supportedJavascriptExtensions, extension => fileExtensionIs(fileName, extension));
     }
 
-    export function isTsx(fileName: string) {
-        return fileExtensionIs(fileName, ".tsx");
-    }
-
     /**
      * Replace each instance of non-ascii characters by one, two, three, or four escape sequences
      * representing the UTF-8 encoding of the character, and return the expanded char code list.
diff --git a/tests/baselines/reference/jsFileCompilationTypeAssertions.errors.txt b/tests/baselines/reference/jsFileCompilationTypeAssertions.errors.txt
index 669e83688cc..50d6416a62b 100644
--- a/tests/baselines/reference/jsFileCompilationTypeAssertions.errors.txt
+++ b/tests/baselines/reference/jsFileCompilationTypeAssertions.errors.txt
@@ -1,9 +1,9 @@
 error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
-tests/cases/compiler/a.js(1,27): error TS17002: Expected corresponding JSX closing tag for 'string'.
+tests/cases/compiler/a.js(1,10): error TS8016: 'type assertion expressions' can only be used in a .ts file.
 
 
 !!! error TS5055: Cannot write file 'tests/cases/compiler/a.js' which is one of the input files.
 ==== tests/cases/compiler/a.js (1 errors) ====
     var v = <string>undefined;
-                              
-!!! error TS17002: Expected corresponding JSX closing tag for 'string'.
\ No newline at end of file
+             ~~~~~~
+!!! error TS8016: 'type assertion expressions' can only be used in a .ts file.
\ No newline at end of file
diff --git a/tests/cases/fourslash/getJavaScriptSemanticDiagnostics20.ts b/tests/cases/fourslash/getJavaScriptSemanticDiagnostics20.ts
index 5172ee7701c..c0c519cb24c 100644
--- a/tests/cases/fourslash/getJavaScriptSemanticDiagnostics20.ts
+++ b/tests/cases/fourslash/getJavaScriptSemanticDiagnostics20.ts
@@ -4,13 +4,13 @@
 // @Filename: a.js
 //// var v = <string>undefined;
 
-verify.getSyntacticDiagnostics(`[
+verify.getSyntacticDiagnostics(`[]`);
+verify.getSemanticDiagnostics(`[
   {
-    "message": "Expected corresponding JSX closing tag for 'string'.",
-    "start": 26,
-    "length": 0,
+    "message": "'type assertion expressions' can only be used in a .ts file.",
+    "start": 9,
+    "length": 6,
     "category": "error",
-    "code": 17002
+    "code": 8016
   }
-]`);
-verify.getSemanticDiagnostics(`[]`);
\ No newline at end of file
+]`);
\ No newline at end of file