diff --git a/tools/tests/test_pr_overlap_export_cache.py b/tools/tests/test_pr_overlap_export_cache.py
index c66efe5232..6ddcdc5365 100644
--- a/tools/tests/test_pr_overlap_export_cache.py
+++ b/tools/tests/test_pr_overlap_export_cache.py
@@ -13,7 +13,7 @@ import pr_overlap
 
 def run(*args):
     return subprocess.run(["git", "-c", "user.name=t", "-c", "user.email=t@t", *args],
-                          capture_output=True, text=True, check=True).stdout.strip()
+                          capture_output=True, encoding="utf-8", check=True).stdout.strip()
 
 
 def write(path, text):