diff --git a/lib/build/bundled-source.js b/lib/build/bundled-source.js
index 14ff2f8ca..6bbb38877 100644
--- a/lib/build/bundled-source.js
+++ b/lib/build/bundled-source.js
@@ -91,7 +91,7 @@ exports.BundledSource = class {
     this.file = file;
     this._contents = null;
     this.requiresTransform = true;
-    this.includedIn.requiresBuild = true;
+    if (this.includedIn) this.includedIn.requiresBuild = true;
   }
 
   transform() {