diff --git a/bin/thumb_server.sh b/bin/thumb_server.sh
index 58dffe4..25daee7 100755
--- a/bin/thumb_server.sh
+++ b/bin/thumb_server.sh
@@ -51,7 +51,7 @@ mkdir -p "../cache/img/$startPath"
 if [ ! $waitForResult ]
 then
     sleep $randomSleep
-    while [[ `ps -e | grep -v grep | grep phantomjs | wc -l` -ge $maxThread ]]
+    while [[ `ps -ax | grep -v grep | grep phantomjs | wc -l` -ge $maxThread ]]
     do
         sleep $randomSleep
     done