diff --git a/letsencrypt-auto-source/Dockerfile.centos6 b/letsencrypt-auto-source/Dockerfile.centos6
index 1bdb23574..f152e1bac 100644
--- a/letsencrypt-auto-source/Dockerfile.centos6
+++ b/letsencrypt-auto-source/Dockerfile.centos6
@@ -33,7 +33,8 @@ COPY . /home/lea/certbot/letsencrypt-auto-source
 # Tweak uname binary for tests on fake 32bits
 COPY tests/uname_wrapper.sh /bin
 RUN mv /bin/uname /bin/uname_orig \
- && mv /bin/uname_wrapper.sh /bin/uname
+ && mv /bin/uname_wrapper.sh /bin/uname \
+ && chmod +x /bin/uname
 
 USER lea
 WORKDIR /home/lea