diff --git a/api-ref/source/conf.py b/api-ref/source/conf.py
index e2dd58c72ec8..c92859261a85 100644
--- a/api-ref/source/conf.py
+++ b/api-ref/source/conf.py
@@ -154,8 +154,7 @@ pygments_style = 'sphinx'
 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].decode()
+    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".')
diff --git a/doc/source/conf.py b/doc/source/conf.py
index 501ab34c4096..84cf3186a6a0 100644
--- a/doc/source/conf.py
+++ b/doc/source/conf.py
@@ -195,8 +195,7 @@ html_static_path = ['_static']
 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].decode()
+    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".')
diff --git a/placement-api-ref/source/conf.py b/placement-api-ref/source/conf.py
index 73d1e01edadc..80a4a5f96542 100644
--- a/placement-api-ref/source/conf.py
+++ b/placement-api-ref/source/conf.py
@@ -156,8 +156,7 @@ pygments_style = 'sphinx'
 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].decode()
+    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".')