diff --git a/src/compiler/factory.ts b/src/compiler/factory.ts
index f7aa18fa7ea..0fd423d342c 100644
--- a/src/compiler/factory.ts
+++ b/src/compiler/factory.ts
@@ -1204,7 +1204,7 @@ namespace ts {
     // Utilities
 
     function isUseStrictPrologue(node: ExpressionStatement): boolean {
-        return !!(node.expression as StringLiteral).text.match(/use strict/);
+        return (node.expression as StringLiteral).text === "use strict";
     }
 
     export function addPrologueDirectives(target: Statement[], source: Statement[], ensureUseStrict?: boolean): number {