1 files changed, 4 insertions, 1 deletions
diff --git a/src/group.cc b/src/group.cc
index 549a4fd..5ce4901 100644
--- a/src/group.cc
+++ b/src/group.cc
@@ -145,7 +145,10 @@ void* ncclAsyncThreadPreconnect(void* args_) {
 
 NCCL_API(ncclResult_t, ncclGroupEnd);
 ncclResult_t ncclGroupEnd() {
-  if (ncclGroupMode == 0) return ncclInvalidUsage;
+  if (ncclGroupMode == 0) {
+    WARN("ncclGroupEnd: not in a group call.");
+    return ncclInvalidUsage;
+  }
   ncclGroupMode--;
   if (ncclGroupMode > 0) return ncclSuccess;
   int savedDev;