diff --git a/Dockerfile-debian.template b/Dockerfile-alpine.template
index 2b39553..0bda827 100644
--- a/Dockerfile-debian.template
+++ b/Dockerfile-alpine.template
@@ -1,18 +1,30 @@
 FROM php:%%PHP_VERSION%%-%%VARIANT%%
 
+# our docker-entrypoint.sh is a bit involved
+RUN apk add --no-cache bash
+# in theory, it is POSIX-compliant, but first priority is a working, consistent image
+
 # install the PHP extensions we need
 RUN set -ex; \
        \
-       apt-get update; \
-       apt-get install -y \
-               libjpeg-dev \
-               libpng12-dev \
+       apk add --no-cache --virtual .build-deps \
+               libjpeg-turbo-dev \
+               libpng-dev \
        ; \
-       rm -rf /var/lib/apt/lists/*; \
        \
        docker-php-ext-configure gd --with-png-dir=/usr --with-jpeg-dir=/usr; \
-       docker-php-ext-install gd mysqli opcache
-# TODO consider removing the *-dev deps and only keeping the necessary lib* packages
+       docker-php-ext-install gd mysqli opcache; \
+       \
+       runDeps="$( \
+               scanelf --needed --nobanner --recursive \
+                       /usr/local/lib/php/extensions \
+                       | awk '{ gsub(/,/, "\nso:", $2); print "so:" $2 }' \
+                       | sort -u \
+                       | xargs -r apk info --installed \
+                       | sort -u \
+       )"; \
+       apk add --virtual .wordpress-phpexts-rundeps $runDeps; \
+       apk del .build-deps
 
 # set recommended PHP.ini settings
 # see https://secure.php.net/manual/en/opcache.installation.php