diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 4335b6fe2f0..212de3a2159 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -16384,6 +16384,10 @@ namespace ts {
         }
 
         function checkNonNullAssertion(node: NonNullExpression) {
+            if (isInJavaScriptFile(node)) {
+                error(node, Diagnostics.non_null_assertions_can_only_be_used_in_a_ts_file);
+            }
+
             return getNonNullableType(checkExpression(node.expression));
         }
 
diff --git a/src/compiler/diagnosticMessages.json b/src/compiler/diagnosticMessages.json
index 1ffc78134c3..3b4b0ddf667 100644
--- a/src/compiler/diagnosticMessages.json
+++ b/src/compiler/diagnosticMessages.json
@@ -3459,6 +3459,10 @@
         "category": "Error",
         "code": 8012
     },
+    "'non-null assertions' can only be used in a .ts file.": {
+        "category": "Error",
+        "code": 8013
+    },
     "'enum declarations' can only be used in a .ts file.": {
         "category": "Error",
         "code": 8015
diff --git a/tests/baselines/reference/jsFileCompilationNonNullAssertion.errors.txt b/tests/baselines/reference/jsFileCompilationNonNullAssertion.errors.txt
new file mode 100644
index 00000000000..13670601f70
--- /dev/null
+++ b/tests/baselines/reference/jsFileCompilationNonNullAssertion.errors.txt
@@ -0,0 +1,8 @@
+/src/a.js(1,1): error TS8013: 'non-null assertions' can only be used in a .ts file.
+
+
+==== /src/a.js (1 errors) ====
+    0!
+    ~~
+!!! error TS8013: 'non-null assertions' can only be used in a .ts file.
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/jsFileCompilationNonNullAssertion.js b/tests/baselines/reference/jsFileCompilationNonNullAssertion.js
new file mode 100644
index 00000000000..3790ff66c17
--- /dev/null
+++ b/tests/baselines/reference/jsFileCompilationNonNullAssertion.js
@@ -0,0 +1,6 @@
+//// [a.js]
+0!
+
+
+//// [a.js]
+0;
diff --git a/tests/cases/compiler/jsFileCompilationNonNullAssertion.ts b/tests/cases/compiler/jsFileCompilationNonNullAssertion.ts
new file mode 100644
index 00000000000..cbe21e91dc6
--- /dev/null
+++ b/tests/cases/compiler/jsFileCompilationNonNullAssertion.ts
@@ -0,0 +1,5 @@
+// @allowJs: true
+// @checkJs: true
+// @filename: /src/a.js
+// @out: /bin/a.js
+0!