diff --git a/config-drive/master_config.yaml b/config-drive/master_config.yaml
index 5f1dbdc..82884f1 100644
--- a/config-drive/master_config.yaml
+++ b/config-drive/master_config.yaml
@@ -162,7 +162,7 @@
         if [ -n "${NOT_PULLED}" ]; then
           echo "Images ${NOT_PULLED} are not pulled yet"
           sleep 10;
-          (( counter++ ))
+          counter=$((counter+1))
         fi
       done
     }