diff --git a/lib/workers/repository/onboarding/branch/config.js b/lib/workers/repository/onboarding/branch/config.js
index de9d0f6ada0da869625d2311b13922dcaa3c82b7..e334a79caf84ad66e4485634babb81ef490c7bc2 100644
--- a/lib/workers/repository/onboarding/branch/config.js
+++ b/lib/workers/repository/onboarding/branch/config.js
@@ -25,9 +25,10 @@ async function getOnboardingConfig(config) {
     }
     if (branchName) {
       logger.info({ branch: branchName }, 'Migrating Greenkeeper branchName');
-      onboardingConfig.branchName = [
-        String(branchName).replace('greenkeeper', appSlug),
-      ];
+      onboardingConfig.branchName = String(branchName).replace(
+        'greenkeeper',
+        appSlug
+      );
     }
     if (is.nonEmptyArray(ignore)) {
       logger.info({ ignore }, 'Migrating Greenkeeper ignore');
diff --git a/test/workers/repository/onboarding/branch/__snapshots__/index.spec.js.snap b/test/workers/repository/onboarding/branch/__snapshots__/index.spec.js.snap
index 2c9fb48170db4bb75978a208472fda4bb5058837..c7ea67e145aaf8905e65570a40c8ed343d83aea7 100644
--- a/test/workers/repository/onboarding/branch/__snapshots__/index.spec.js.snap
+++ b/test/workers/repository/onboarding/branch/__snapshots__/index.spec.js.snap
@@ -6,9 +6,7 @@ exports[`workers/repository/onboarding/branch checkOnboardingBranch creates onbo
   \\"labels\\": [
     \\"renovate\\"
   ],
-  \\"branchName\\": [
-    \\"renovate--\\"
-  ],
+  \\"branchName\\": \\"renovate--\\",
   \\"ignoreDeps\\": [
     \\"foo\\",
     \\"bar\\"