diff --git a/Dockerfile-debian.template b/Dockerfile-debian.template
index a615ac022e..56c9b75ae8 100644
--- a/Dockerfile-debian.template
+++ b/Dockerfile-debian.template
@@ -205,6 +205,7 @@ RUN set -eux; \
 # update pecl channel definitions https://github.com/docker-library/php/issues/443
 	pecl update-channels; \
 	rm -rf /tmp/pear ~/.pearrc; \
+	rm -rf /usr/src/* /var/cache/debconf; \
 # smoke test
 	php --version