diff --git a/doc/source/conf.py b/doc/source/conf.py
index cda0c77ea..a6f84e190 100644
--- a/doc/source/conf.py
+++ b/doc/source/conf.py
@@ -151,8 +151,7 @@ modindex_common_prefix = ['keystoneclient.']
 git_cmd = ["git", "log", "--pretty=format:'%ad, commit %h'", "--date=local",
            "-n1"]
 try:
-    html_last_updated_fmt = subprocess.Popen(git_cmd,
-                                     stdout=subprocess.PIPE).communicate()[0]
+    html_last_updated_fmt = subprocess.check_output(git_cmd).decode('utf-8')
 except Exception:
     warnings.warn('Cannot get last updated time from git repository. '
                   'Not setting "html_last_updated_fmt".')