diff --git a/lib/manager/bundler/artifacts.ts b/lib/manager/bundler/artifacts.ts
index f5ebc96f9d8bd39cb3b3b7a3a47ec4b9a3744eb4..489a69aa2dba92861203d0491c2355fb5e8df492 100644
--- a/lib/manager/bundler/artifacts.ts
+++ b/lib/manager/bundler/artifacts.ts
@@ -135,7 +135,7 @@ export async function updateArtifacts(
       },
     ];
   } catch (err) /* istanbul ignore next */ {
-    if (err.stderr && err.stderr.startsWith('fatal: Could not parse object')) {
+    if (err.message.includes('fatal: Could not parse object')) {
       return [
         {
           artifactError: {