diff --git a/_action_files/fastpages-nbdev.Dockerfile b/_action_files/fastpages-nbdev.Dockerfile
old mode 100755
new mode 100644
index 2993547..aeffb54
--- a/_action_files/fastpages-nbdev.Dockerfile
+++ b/_action_files/fastpages-nbdev.Dockerfile
@@ -1,4 +1,4 @@
-FROM python:3-slim-stretch
+FROM python:3.7-slim-stretch
 
 RUN pip install --upgrade pip
 RUN apt-get update; apt-get -y install wget git jq dos2unix curl