diff --git a/integration-tests/test_extensions.py b/integration-tests/test_extensions.py
index fdc1653..850096a 100644
--- a/integration-tests/test_extensions.py
+++ b/integration-tests/test_extensions.py
@@ -41,6 +41,6 @@ def test_labextensions():
     for e in extensions:
         # jupyter labextension lists outputs to stderr
         out = proc.stderr.decode()
-        enabled_ok_pattern = re.compile(fr"{e}.*enabled.*OK")
+        enabled_ok_pattern = re.compile(rf"{e}.*enabled.*OK")
         matches = enabled_ok_pattern.search(out)
         assert matches is not None