diff --git a/doc/source/conf.py b/doc/source/conf.py
index b043bd528d..dce017e74f 100644
--- a/doc/source/conf.py
+++ b/doc/source/conf.py
@@ -15,9 +15,9 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import sys
-
 import os
+import subprocess
+import sys
 
 on_rtd = os.environ.get('READTHEDOCS', None) == 'True'
 
@@ -148,8 +148,10 @@ html_static_path = ['_static']
 # 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.