diff --git a/src/copapy/_basic_types.py b/src/copapy/_basic_types.py
index 915dcef..1d8ce67 100644
--- a/src/copapy/_basic_types.py
+++ b/src/copapy/_basic_types.py
@@ -322,9 +322,11 @@ def iif(expression: variable[Any], true_result: unifloat, false_result: unifloat
 @overload
 def iif(expression: float | int, true_result: TNum, false_result: TNum) -> TNum: ...
 @overload
-def iif(expression: float | int, true_result: TNum, false_result: variable[TNum]) -> variable[TNum]: ...
+def iif(expression: float | int, true_result: TNum | variable[TNum], false_result: variable[TNum]) -> variable[TNum]: ...
 @overload
 def iif(expression: float | int, true_result: variable[TNum], false_result: TNum | variable[TNum]) -> variable[TNum]: ...
+@overload
+def iif(expression: float | int | variable[Any], true_result: TNum | variable[TNum], false_result: TNum | variable[TNum]) -> variable[TNum] | TNum: ...
 def iif(expression: Any, true_result: Any, false_result: Any) -> Any:
     allowed_type = (variable, int, float)
     assert isinstance(true_result, allowed_type) and isinstance(false_result, allowed_type), "Result type not supported"