diff --git a/doc/source/conf.py b/doc/source/conf.py
index 2bf0f0f..5293561 100644
--- a/doc/source/conf.py
+++ b/doc/source/conf.py
@@ -1,6 +1,7 @@
 
 from __future__ import print_function
 
+import subprocess
 import sys
 import os
 import fileinput
@@ -60,8 +61,10 @@ pygments_style = 'sphinx'
 # Output file base name for HTML help builder.
 htmlhelp_basename = '%sdoc' % project
 
-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]
 
 # Grouping the document tree into LaTeX files. List of tuples
 # (source start file, target name, title, author, documentclass