diff --git a/packages/nx/src/plugins/js/lock-file/yarn-parser.ts b/packages/nx/src/plugins/js/lock-file/yarn-parser.ts
index dca2e78a2cc51..271d5246a4506 100644
--- a/packages/nx/src/plugins/js/lock-file/yarn-parser.ts
+++ b/packages/nx/src/plugins/js/lock-file/yarn-parser.ts
@@ -362,7 +362,10 @@ function mapSnapshots(
           .slice(0, key.indexOf('#'))
           .replace(`@patch:${packageName}@`, '@npm:');
       }
-      if (!existingKeys.get(packageName).has(normalizedKey)) {
+      if (
+        !existingKeys.get(packageName) ||
+        !existingKeys.get(packageName).has(normalizedKey)
+      ) {
         keysSet.delete(key);
       }
     }