diff --git a/local-cli/server/util/debugger-ui/deltaUrlToBlobUrl.js b/local-cli/server/util/debugger-ui/deltaUrlToBlobUrl.js
index e57b7e42f..5a206ce22 100644
--- a/local-cli/server/util/debugger-ui/deltaUrlToBlobUrl.js
+++ b/local-cli/server/util/debugger-ui/deltaUrlToBlobUrl.js
@@ -49,7 +49,11 @@
       URL.revokeObjectURL(cachedBundle.url);
     }
 
-    const blobContent = deltaPatcher.getAllModules();
+    // To make Source Maps work correctly, we need to add a newline between
+    // modules.
+    const blobContent = deltaPatcher
+      .getAllModules()
+      .map(module => module + '\n');
 
     // Build the blob with the whole JS bundle.
     const blob = new Blob(blobContent, {