diff --git a/rhodecode/lib/rc_cache/cache_key_meta.py b/rhodecode/lib/rc_cache/cache_key_meta.py
--- a/rhodecode/lib/rc_cache/cache_key_meta.py
+++ b/rhodecode/lib/rc_cache/cache_key_meta.py
@@ -38,7 +38,7 @@ def free_cache_keys(*args):
 
     if cache_keys_by_pid:
         try:
-            for cache_proc in cache_keys_by_pid:
+            for cache_proc in set(cache_keys_by_pid):
                 like_expression = '{}%'.format(cache_proc)
                 CacheKey.query().filter(
                     CacheKey.cache_key.like(like_expression)).delete(synchronize_session='fetch')