diff --git a/packages/metro/src/lib/SourceMap.js b/packages/metro/src/lib/SourceMap.js
index 453c049f..5851f2b9 100644
--- a/packages/metro/src/lib/SourceMap.js
+++ b/packages/metro/src/lib/SourceMap.js
@@ -23,7 +23,10 @@ export type IndexMapSection = {
 
 export type RawMappings = Array<RawMapping>;
 
-type FBExtensions = {x_facebook_offsets: Array<number>};
+type FBExtensions = {
+  x_facebook_offsets: Array<number>,
+  x_metro_module_paths: Array<string>,
+};
 
 export type {MappingsMap};
 export type IndexMap = {
diff --git a/packages/metro/src/shared/output/unbundle/build-unbundle-sourcemap-with-metadata.js b/packages/metro/src/shared/output/unbundle/build-unbundle-sourcemap-with-metadata.js
index ede170b4..0c727198 100644
--- a/packages/metro/src/shared/output/unbundle/build-unbundle-sourcemap-with-metadata.js
+++ b/packages/metro/src/shared/output/unbundle/build-unbundle-sourcemap-with-metadata.js
@@ -41,11 +41,22 @@ module.exports = ({
     sourcePath: '',
   };
 
+  // Add map of module id -> source to sourcemap
+  const module_paths = [];
+  startupModules.forEach(m => {
+    module_paths[m.id] = m.sourcePath;
+  });
+  lazyModules.forEach(m => {
+    module_paths[m.id] = m.sourcePath;
+  });
+
   const map = combineSourceMapsAddingOffsets(
     [startupModule].concat(lazyModules),
+    module_paths,
     moduleGroups,
     options,
   );
   delete map.x_facebook_offsets[Number.MIN_SAFE_INTEGER];
+
   return map;
 };
diff --git a/packages/metro/src/shared/output/unbundle/util.js b/packages/metro/src/shared/output/unbundle/util.js
index 3b4d565b..cc946cbf 100644
--- a/packages/metro/src/shared/output/unbundle/util.js
+++ b/packages/metro/src/shared/output/unbundle/util.js
@@ -66,6 +66,7 @@ function combineSourceMaps(
 
 function combineSourceMapsAddingOffsets(
   modules: $ReadOnlyArray<ModuleTransportLike | RamModule>,
+  x_metro_module_paths: Array<string>,
   moduleGroups?: ?ModuleGroups,
   options?: ?CombineOptions,
 ): FBIndexMap {
@@ -76,7 +77,7 @@ function combineSourceMapsAddingOffsets(
     moduleGroups,
     options,
   );
-  return {sections, version: 3, x_facebook_offsets};
+  return {sections, version: 3, x_facebook_offsets, x_metro_module_paths};
 }
 
 function combineMaps(