diff --git a/testing/test_warnings.py b/testing/test_warnings.py
index 467753b6a6e..4800a916eac 100644
--- a/testing/test_warnings.py
+++ b/testing/test_warnings.py
@@ -440,7 +440,7 @@ def test():
             pass
     """
     )
-    result = pytester.runpytest("-W", "ignore::bizbaz.Bizbaz")
+    result = pytester.runpytest_subprocess("-W", "ignore::bizbaz.Bizbaz")
     result.stdout.fnmatch_lines(
         [
             f"*== {WARNINGS_SUMMARY_HEADER} ==*",