diff --git a/src/harness/fourslash.ts b/src/harness/fourslash.ts
index f8086d0ed52..259fcbefac2 100644
--- a/src/harness/fourslash.ts
+++ b/src/harness/fourslash.ts
@@ -18,6 +18,8 @@
 /// <reference path='harness.ts' />
 
 module FourSlash {
+    ts.disableIncrementalParsing = false;
+
     // Represents a parsed source file with metadata
     export interface FourSlashFile {
         // The contents of the file (with markers, etc stripped out)
diff --git a/src/services/services.ts b/src/services/services.ts
index 757e1b62083..f8070fa0531 100644
--- a/src/services/services.ts
+++ b/src/services/services.ts
@@ -1553,7 +1553,7 @@ module ts {
         return sourceFile;
     }
 
-    export var disableIncrementalParsing = false;
+    export var disableIncrementalParsing = true;
 
     export function updateLanguageServiceSourceFile(sourceFile: SourceFile, scriptSnapshot: IScriptSnapshot, version: string, isOpen: boolean, textChangeRange: TextChangeRange): SourceFile {
         if (textChangeRange && Debug.shouldAssert(AssertionLevel.Normal)) {
diff --git a/tests/cases/unittests/incrementalParser.ts b/tests/cases/unittests/incrementalParser.ts
index 263c396842d..a3875cf8e8c 100644
--- a/tests/cases/unittests/incrementalParser.ts
+++ b/tests/cases/unittests/incrementalParser.ts
@@ -2,6 +2,8 @@
 /// <reference path="..\..\..\src\compiler\parser.ts" />
 
 module ts {
+    ts.disableIncrementalParsing = false;
+
     function withChange(text: IScriptSnapshot, start: number, length: number, newText: string): { text: IScriptSnapshot; textChangeRange: TextChangeRange; } {
         var contents = text.getText(0, text.getLength());
         var newContents = contents.substr(0, start) + newText + contents.substring(start + length);