diff --git a/pandas/tests/groupby/transform/test_transform.py b/pandas/tests/groupby/transform/test_transform.py
index 237d6a96f39ec..0492b143eaf1f 100644
--- a/pandas/tests/groupby/transform/test_transform.py
+++ b/pandas/tests/groupby/transform/test_transform.py
@@ -1043,7 +1043,7 @@ def demean_rename(x):
         if isinstance(x, Series):
             return result
 
-        result = result.rename(columns={c: "{c}_demeaned" for c in result.columns})
+        result = result.rename(columns={c: f"{c}_demeaned" for c in result.columns})
 
         return result