diff --git a/spec/src/full.spec.ts b/spec/src/full.spec.ts
index bd96f17..25b0c2e 100644
--- a/spec/src/full.spec.ts
+++ b/spec/src/full.spec.ts
@@ -844,6 +844,39 @@ CLASS Dog INHERITS Animal
 	ENDFUNCTION
 ENDCLASS
 
+DECLARE animal: Animal
+animal <- NEW Animal("animal")
+DECLARE dog: Dog
+dog <- NEW Dog("doggy")
+DECLARE dogAnimal: Animal
+dogAnimal <- NEW Dog("doggy2")
+PROCEDURE test(arg:Animal)
+	OUTPUT arg.isSus()
+ENDPROCEDURE
+CALL test(animal)
+CALL test(dog)
+CALL test(dogAnimal)`,
+["TRUE", "FALSE", "FALSE"]
+],
+call_class_method_in_function_polymorphically_and_mutate_byref: [
+`CLASS Animal
+	PUBLIC Name: STRING
+	PUBLIC PROCEDURE NEW(name: STRING)
+		Name <- name
+	ENDPROCEDURE
+	PUBLIC FUNCTION isSus() RETURNS BOOLEAN
+		RETURN TRUE
+	ENDFUNCTION
+ENDCLASS
+CLASS Dog INHERITS Animal
+	PUBLIC PROCEDURE NEW(name: STRING)
+		CALL SUPER.NEW(name)
+	ENDPROCEDURE
+	PUBLIC FUNCTION isSus() RETURNS BOOLEAN
+		RETURN FALSE
+	ENDFUNCTION
+ENDCLASS
+
 DECLARE animal: Animal
 animal <- NEW Animal("animal")
 DECLARE dog: Dog
@@ -856,7 +889,7 @@ ENDPROCEDURE
 CALL test(animal)
 CALL test(dog)
 CALL test(dogAnimal)`,
-["TRUE", "FALSE", "FALSE"]
+`Cannot coerce BYREF`
 ],
 call_class_method_in_function_polymorphically_and_mutate_byval: [
 `CLASS Animal