diff --git a/src/libCom/osi/devLib.c b/src/libCom/osi/devLib.c
index a8e9e5fe3..ac999c9ff 100644
--- a/src/libCom/osi/devLib.c
+++ b/src/libCom/osi/devLib.c
@@ -466,7 +466,7 @@ long devUnregisterAddress(
     devInsertAddress (&addrFree[addrType], pRange);
     s = devCombineAdjacentBlocks (&addrFree[addrType], pRange);
     if(s){
-        errMessage (s, NULL);
+        errMessage (s, "devCombineAdjacentBlocks error");
         return s;
     }