diff --git a/rootfs/usr/local/bin/startup b/rootfs/usr/local/bin/startup
index f0853fb..81af2db 100644
--- a/rootfs/usr/local/bin/startup
+++ b/rootfs/usr/local/bin/startup
@@ -33,8 +33,8 @@ fi
 
 # Install additional php extensions
 if [ -n "${PHP_EXTENSIONS}" ]; then
-  for extension in ${PHP_EXTENSIONS}; do
-    PACKAGES="php7-${extension} ${PACKAGES}"
+  for php_extension in ${PHP_EXTENSIONS}; do
+    PACKAGES="php7-${php_extension} ${PACKAGES}"
   done
 
   apk add --no-progress --no-cache ${PACKAGES}