diff --git a/tests/checkpatch.at b/tests/checkpatch.at
index fa179c707..2ed2ec878 100755
--- a/tests/checkpatch.at
+++ b/tests/checkpatch.at
@@ -29,11 +29,13 @@ Subject: Patch this is.
     fi
 
     if test -s expout; then
-        AT_CHECK([$PYTHON3 $top_srcdir/utilities/checkpatch.py $3 -q test.patch],
+        AT_CHECK([OVS_SRC_DIR=$top_srcdir $PYTHON3 \
+                    $top_srcdir/utilities/checkpatch.py $3 -q test.patch],
                  [1], [stdout])
         AT_CHECK([sed '/^Lines checked:/,$d' stdout], [0], [expout])
     else
-        AT_CHECK([$PYTHON3 $top_srcdir/utilities/checkpatch.py $3 -q test.patch])
+        AT_CHECK([OVS_SRC_DIR=$top_srcdir $PYTHON3 \
+                    $top_srcdir/utilities/checkpatch.py $3 -q test.patch])
     fi
 }
 OVS_END_SHELL_HELPERS
diff --git a/utilities/checkpatch.py b/utilities/checkpatch.py
index 53b13bcf2..fe6aa79b0 100755
--- a/utilities/checkpatch.py
+++ b/utilities/checkpatch.py
@@ -18,6 +18,7 @@ import email
 import getopt
 import os
 import re
+import subprocess
 import sys
 
 RETURN_CHECK_INITIAL_STATE = 0
@@ -867,13 +868,14 @@ def run_subject_checks(subject, spellcheck=False):
 
 
 def get_top_directory():
-    with os.popen('git rev-parse --show-toplevel') as pipe:
-        path = pipe.read()
+    result = subprocess.run('git rev-parse --show-toplevel',
+                            stdout=subprocess.PIPE,
+                            stderr=subprocess.DEVNULL, shell=True)
 
-    if path:
-        return path.strip()
+    if result and result.returncode == 0:
+        return result.stdout.decode('utf-8').strip()
 
-    return "."
+    return os.getenv('OVS_SRC_DIR', '.')
 
 
 def update_missing_authors(diffed_line):