diff --git a/Adapter.cc b/Adapter.cc
index 88d1e4b..46e52c2 100644
--- a/Adapter.cc
+++ b/Adapter.cc
@@ -36,7 +36,7 @@ namespace pEp {
         notifyHandshake_t _notifyHandshake = nullptr;
         std::thread *_sync_thread = nullptr;
 
-        ::utility::locked_queue< SYNC_EVENT > q;
+        ::utility::locked_queue< SYNC_EVENT, &free_Sync_event> q;
         std::mutex m;
 
         int _inject_sync_event(SYNC_EVENT ev, void *management)
diff --git a/Adapter.hxx b/Adapter.hxx
index b98e283..0ab39b6 100644
--- a/Adapter.hxx
+++ b/Adapter.hxx
@@ -10,7 +10,7 @@ namespace pEp {
         extern notifyHandshake_t _notifyHandshake;
         extern std::thread *_sync_thread;
 
-        extern ::utility::locked_queue< SYNC_EVENT > q;
+        extern ::utility::locked_queue< SYNC_EVENT, &free_Sync_event > q;
         extern std::mutex m;
 
         SYNC_EVENT _retrieve_next_sync_event(void *management, time_t threshold);