diff --git a/tools/isobuild/resolver.js b/tools/isobuild/resolver.js
index b838282fa2..a5f48a79ff 100644
--- a/tools/isobuild/resolver.js
+++ b/tools/isobuild/resolver.js
@@ -204,7 +204,9 @@ export default class Resolver {
   }
 
   _resolveNodeModule(id, absParentPath) {
-    let resolved = null;
+    if (! Resolver.isTopLevel(id)) {
+      return null;
+    }
 
     if (Resolver.isNative(id) &&
         archMatches(this.targetArch, "os")) {
@@ -234,6 +236,8 @@ export default class Resolver {
       }
     });
 
+    let resolved = null;
+
     if (sourceRoot) {
       let dir = absParentPath; // It's ok for absParentPath to be a directory!
       let info = this._joinAndStat(dir);