diff --git a/doc/source/conf.py b/doc/source/conf.py
index 2621e039c..4983b9c3e 100644
--- a/doc/source/conf.py
+++ b/doc/source/conf.py
@@ -135,8 +135,7 @@ html_theme = 'nature'
 # using the given strftime format.
 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]
+html_last_updated_fmt = subprocess.check_output(git_cmd).decode('utf-8')
 
 # If true, SmartyPants will be used to convert quotes and dashes to
 # typographically correct entities.