diff --git a/src/services/services.ts b/src/services/services.ts
index 092f987eb5a..4109a4eb345 100644
--- a/src/services/services.ts
+++ b/src/services/services.ts
@@ -1948,7 +1948,7 @@ namespace ts {
         return sourceFile;
     }
 
-    export const disableIncrementalParsing = false;
+    export let disableIncrementalParsing = false;
 
     export function updateLanguageServiceSourceFile(sourceFile: SourceFile, scriptSnapshot: IScriptSnapshot, version: string, textChangeRange: TextChangeRange, aggressiveChecks?: boolean): SourceFile {
         // If we were given a text change range, and our version or open-ness changed, then