diff --git a/src/code-split.js b/src/code-split.js
index 723bae6..bd8e5b6 100644
--- a/src/code-split.js
+++ b/src/code-split.js
@@ -207,10 +207,10 @@ const isHydratable = (hydratablePropPath)=> (
 );
 
 
-const getAst = (source, inputSourceMap)=> (
+const getAst = (source, sourceMap)=> (
   parse(source, {
     sourceType: 'module',
-    inputSourceMap
+    inputSourceMap: sourceMap || false
   })
 );