diff --git a/src/package-resolver.js b/src/package-resolver.js
index 4cca3a7dfa..3b6b6417ef 100644
--- a/src/package-resolver.js
+++ b/src/package-resolver.js
@@ -348,7 +348,6 @@ export default class PackageResolver {
     }
 
     byName.splice(byName.indexOf(pattern), 1);
-    delete this.patterns[pattern];
   }
 
   /**