diff --git a/doc/source/conf.py b/doc/source/conf.py
index cb229cf..963c33b 100644
--- a/doc/source/conf.py
+++ b/doc/source/conf.py
@@ -12,6 +12,7 @@
 # serve to show the default.
 
 import datetime
+import subprocess
 import sys
 import os
 
@@ -128,8 +129,12 @@ html_theme = 'nature'
 
 # If not '', a 'Last updated on:' timestamp is inserted at every page bottom,
 # using the given strftime format.
-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.
@@ -273,4 +278,4 @@ epub_copyright = u'2015, OpenStack Mistral Team'
 #epub_tocdepth = 3
 
 # Allow duplicate toc entries.
-#epub_tocdup = True
\ No newline at end of file
+#epub_tocdup = True