diff --git a/README.md b/README.md
index 89efb79..75d0961 100644
--- a/README.md
+++ b/README.md
@@ -19,7 +19,7 @@ FROM php:7.2-cli
 
 ADD https://raw.githubusercontent.com/mlocati/docker-php-extension-installer/master/install-php-extensions /usr/local/bin/
 
-RUN chmod uga+x /usr/local/bin/install-php-extensions && \
+RUN chmod uga+x /usr/local/bin/install-php-extensions && sync && \
     install-php-extensions gd xdebug
 ```