diff --git a/thorlcr/thorutil/thormisc.cpp b/thorlcr/thorutil/thormisc.cpp
index 24faa992900..4d774eac2ea 100644
--- a/thorlcr/thorutil/thormisc.cpp
+++ b/thorlcr/thorutil/thormisc.cpp
@@ -1364,8 +1364,9 @@ class CRowServer : public CSimpleInterface, implements IThreaded, implements IRo
 #ifdef TRACE_GLOBAL_GROUP
         ActPrintLog(activity, "%s", __func__);
 #endif
-        running = false;
-        comm.cancel(RANK_ALL, mpTag);
+        bool wanted = true;
+        if (running.compare_exchange_strong(wanted, false))
+            comm.cancel(RANK_ALL, mpTag);
     }
 };