diff --git a/slither/slithir/operations/unary.py b/slither/slithir/operations/unary.py
index a6529d7268..c6493921dc 100644
--- a/slither/slithir/operations/unary.py
+++ b/slither/slithir/operations/unary.py
@@ -58,7 +58,7 @@ def type(self) -> UnaryOperationType:
 
     @property
     def type_str(self):
-        return self._type.value
+        return str(self._type)
 
     def __str__(self):
         return f"{self.lvalue} = {self.type_str} {self.rvalue} "