diff --git a/Dockerfile-php b/Dockerfile-php
index 8ebcfbe..ee53d36 100644
--- a/Dockerfile-php
+++ b/Dockerfile-php
@@ -11,8 +11,8 @@ RUN apt-get install -y --no-install-recommends ca-certificates curl apt-transpor
 
 RUN set -eux; [ ! -d /var/www/html ]; mkdir -p /var/www/html; chown www-data:www-data /var/www/html; chmod 1777 /var/www/html
 
-ENV APACHE_CONFDIR /etc/apache2
-ENV APACHE_ENVVARS $APACHE_CONFDIR/envvars
+ENV APACHE_CONFDIR=/etc/apache2
+ENV APACHE_ENVVARS=$APACHE_CONFDIR/envvars
 
 RUN set -eux; \
 	apt-get install -y --no-install-recommends apache2; \