diff --git a/doc/source/conf.py b/doc/source/conf.py
index 77f0b3bb70d..4f0b7de0a35 100644
--- a/doc/source/conf.py
+++ b/doc/source/conf.py
@@ -28,6 +28,7 @@
 # serve to show the default.
 
 import os
+import subprocess
 import sys
 
 # If extensions (or modules to document with autodoc) are in another directory,
@@ -157,8 +158,11 @@ modindex_common_prefix = ['neutron.']
 # If not '', a 'Last updated on:' timestamp is inserted at every page bottom,
 # using the given strftime format.
 #html_last_updated_fmt = '%b %d, %Y'
-git_cmd = "git log --pretty=format:'%ad, commit %h' --date=local -n1"
-html_last_updated_fmt = os.popen(git_cmd).read()
+git_cmd = ["git", "log", "--pretty=format:'%ad, commit %h'", "--date=local -",
+   "n1"]
+html_last_updated_fmt = subprocess.Popen(git_cmd,
+                                         stdout=subprocess.PIPE).\
+                                         communicate()[0]
 
 # If true, SmartyPants will be used to convert quotes and dashes to
 # typographically correct entities.