diff --git a/gcs/src/gcs_group.cpp b/gcs/src/gcs_group.cpp
index a46b8ca57..e0c128272 100644
--- a/gcs/src/gcs_group.cpp
+++ b/gcs/src/gcs_group.cpp
@@ -61,6 +61,7 @@ gcs_group_init (gcs_group_t* group, gu::Config* const cnf, gcache_t* const cache
                 int const appl_proto_ver)
 {
     // here we also create default node instance.
+    new (&group->memb_mtx_) gu::Mutex(NULL);
     group->cache        = cache;
     group->act_id_      = GCS_SEQNO_ILL;
     group->conf_id      = GCS_SEQNO_ILL;