diff --git a/lib/platform/github/index.js b/lib/platform/github/index.js
index ba1068bbce65f9fe6ae0bebe8997c8604aa2b3b2..6f8b494bab19c3791034b8e48f7bbc254d3041e9 100644
--- a/lib/platform/github/index.js
+++ b/lib/platform/github/index.js
@@ -208,6 +208,7 @@ async function initRepo({
   // istanbul ignore if
   if (mirrorMode) {
     logger.info('Renovate is in mirrorMode');
+    config.mirrorMode = true;
     const parentRepo = res.body.parent.full_name;
     logger.debug('Parent repo is ' + parentRepo);
     const parentDefaultBranch = (await get(`repos/${repository}`)).body
@@ -764,7 +765,16 @@ async function createPr(
   useDefaultBranch,
   statusCheckVerify
 ) {
-  const base = useDefaultBranch ? config.defaultBranch : config.baseBranch;
+  let base = useDefaultBranch ? config.defaultBranch : config.baseBranch;
+  // istanbul ignore if
+  if (config.mirrorMode && branchName === 'renovate/configure') {
+    logger.debug('Using renovate-config as base branch for mirror config');
+    if (!await branchExists('renovate-config')) {
+      const baseCommitSHA = await getBaseCommitSHA();
+      await createBranch('renovate-config', baseCommitSHA);
+    }
+    base = 'renovate-config';
+  }
   // Include the repository owner to handle forkMode and regular mode
   const head = `${config.repository.split('/')[0]}:${branchName}`;
   const options = {