diff --git a/data_structures/stacks/postfix_evaluation.py b/data_structures/stacks/postfix_evaluation.py
index 808162faf..36062abb1 100644
--- a/data_structures/stacks/postfix_evaluation.py
+++ b/data_structures/stacks/postfix_evaluation.py
@@ -88,6 +88,8 @@ def evaluate(post_fix: list[str], verbose: bool = False) -> int | float | str |
     6.6
     >>> evaluate(["2", "-", "3", "+"])
     1
+    >>> evaluate(["-4", "5", "*", "6", "-"])
+    -26
     >>> evaluate([])
     0