diff --git a/run_tempest.sh b/run_tempest.sh
index bdd1f69..5a9b742 100755
--- a/run_tempest.sh
+++ b/run_tempest.sh
@@ -58,7 +58,7 @@
     -l|--logging) logging=1;;
     -L|--logging-config) logging_config=$2; shift;;
     --) [ "yes" == "$first_uu" ] || testrargs="$testrargs $1"; first_uu=no  ;;
-    *) testrargs+="$testrargs $1";;
+    *) testrargs="$testrargs $1";;
   esac
   shift
 done