diff --git a/opal/mca/btl/uct/btl_uct_tl.c b/opal/mca/btl/uct/btl_uct_tl.c
index 0c8f27d923..1c1932e911 100644
--- a/opal/mca/btl/uct/btl_uct_tl.c
+++ b/opal/mca/btl/uct/btl_uct_tl.c
@@ -221,7 +221,7 @@ int mca_btl_uct_process_connection_request (mca_btl_uct_module_t *module, mca_bt
 
         /* to avoid a race with send adding pending frags grab the lock here */
         OPAL_THREAD_SCOPED_LOCK(&endpoint->ep_lock,{
-                BTL_VERBOSE(("connection ready. sending %d frags", opal_list_get_size (&module->pending_frags)));
+                BTL_VERBOSE(("connection ready. sending %" PRIsize_t " frags", opal_list_get_size (&module->pending_frags)));
                 (void) opal_atomic_or_fetch_32 (&tl_endpoint->flags, MCA_BTL_UCT_ENDPOINT_FLAG_CONN_READY);
                 opal_atomic_wmb ();