diff --git a/lib/platform/gitlab/storage.js b/lib/platform/gitlab/storage.js
index 63f0ac79037e85271d353cd5d6fb491b941ec3f5..64f90bb9ff5ed70adfa9314ddce22ba086b8a915 100644
--- a/lib/platform/gitlab/storage.js
+++ b/lib/platform/gitlab/storage.js
@@ -78,7 +78,9 @@ class Storage {
         `projects/${config.repository}/repository/branches?search=${search}`,
         { paginate: true }
       );
-      return allBranches.body.map(branch => branch.name);
+      return allBranches.body
+        .map(branch => branch.name)
+        .filter(branchName => branchName.startsWith(branchPrefix));
     }
 
     async function isBranchStale(branchName) {