diff --git a/plugins/op_waf/t/ngx_debug.sh b/plugins/op_waf/t/ngx_debug.sh
index 06ca5eb56..b4e962c77 100644
--- a/plugins/op_waf/t/ngx_debug.sh
+++ b/plugins/op_waf/t/ngx_debug.sh
@@ -5,7 +5,7 @@
 
 if [ $# -ne 3 ]
 then
-    echo "Usage: ./`basename $0` lua/c PID NAME"
+    echo "Usage: ./`basename $0` lua/c NAME"
     exit
 fi