diff --git a/docker/Dockerfile.f26 b/docker/Dockerfile.f26
index db93f0e..582c7ad 100644
--- a/docker/Dockerfile.f26
+++ b/docker/Dockerfile.f26
@@ -2,8 +2,9 @@
 FROM registry.fedoraproject.org/fedora:26
 MAINTAINER Daniele Viganò <daniele@vigano.me>
 
-RUN dnf install -y sudo tar bzip2 git python3-pip mock copr-cli && \
-    dnf clean all
+RUN dnf install -y sudo findutils tar bzip2 git python3-pip mock copr-cli && \
+    dnf clean all && \
+    find /var/cache/dnf -type d -delete
 # Use a Twisted binary wheel to avoid too many dependencies
 RUN pip3 install https://daniele.vigano.me/files/pypi/Twisted-17.9.0-cp36-cp36m-manylinux1_x86_64.whl \
                  buildbot-worker
diff --git a/docker/Dockerfile.f27 b/docker/Dockerfile.f27
index a6ae1c9..3b4fb71 100644
--- a/docker/Dockerfile.f27
+++ b/docker/Dockerfile.f27
@@ -2,8 +2,9 @@
 FROM registry.fedoraproject.org/fedora:27
 MAINTAINER Daniele Viganò <daniele@vigano.me>
 
-RUN dnf install -y sudo tar bzip2 git python3-pip mock copr-cli && \
-    dnf clean all
+RUN dnf install -y sudo findutils tar bzip2 git python3-pip mock copr-cli && \
+    dnf clean all && \
+    find /var/cache/dnf -type d -delete
 # Use a Twisted binary wheel to avoid too many dependencies
 RUN pip3 install https://daniele.vigano.me/files/pypi/Twisted-17.9.0-cp36-cp36m-manylinux1_x86_64.whl \
                  buildbot-worker