diff --git a/docker/php/Dockerfile b/docker/php/Dockerfile
index a64eb7b905..94e51fb724 100644
--- a/docker/php/Dockerfile
+++ b/docker/php/Dockerfile
@@ -3,7 +3,7 @@ FROM php:fpm-alpine
 RUN apk update && apk add git autoconf make file gettext-dev icu-dev zlib-dev libpng-dev gmp-dev \
         mariadb-dev mariadb-client postgresql-dev postgresql-client composer > /dev/null
 
-ARG exts=" bcmath exif gd gettext gmp intl mysqli opcache pdo pdo_mysql mysqli pdo_pgsql pgsql"
+ARG MAKEFLAGS="-j$(cat /proc/cpuinfo | grep processor | wc -l)"
 
 RUN apk add --virtual .phpize-deps $PHPIZE_DEPS \
         && cd /tmp && git clone https://github.com/krakjoe/apcu && cd apcu && phpize && ./configure --enable-apcu && make install \
@@ -15,6 +15,7 @@ RUN apk add --virtual .phpize-deps $PHPIZE_DEPS \
         && rm -rf /tmp/* \
         && apk del .phpize-deps > /dev/null
 
-RUN docker-php-ext-install ${exts} && docker-php-ext-enable ds msgpack redis apcu
+RUN docker-php-ext-install bcmath exif gd gettext gmp intl mysqli opcache pdo pdo_mysql mysqli pdo_pgsql pgsql \
+    && docker-php-ext-enable ds msgpack redis apcu
 
 WORKDIR /var/www/social