diff --git a/src/info.cpp b/src/info.cpp
index ffae037f7..5a1606088 100644
--- a/src/info.cpp
+++ b/src/info.cpp
@@ -118,6 +118,7 @@ void FState::SetAction(const char *name)
 	ActionFunc = FindVMFunction(RUNTIME_CLASS(AActor), name);
 }
 
+
 bool FState::CallAction(AActor *self, AActor *stateowner, FStateParamInfo *info, FState **stateret)
 {
 	if (ActionFunc != nullptr)
@@ -140,6 +141,34 @@ bool FState::CallAction(AActor *self, AActor *stateowner, FStateParamInfo *info,
 		}
 		try
 		{
+			auto CheckType = [=](AActor *check, PType *requiredType)
+			{
+				// This should really never happen. Any valid action function must have actor pointers here.
+				if (!requiredType->isObjectPointer())
+				{
+					ThrowAbortException(X_OTHER, "Bad function prototype in function call to %s", ActionFunc->PrintableName.GetChars());
+				}
+				auto cls = static_cast<PObjectPointer*>(requiredType)->PointedClass();
+				if (!check->IsKindOf(cls))
+				{
+					ThrowAbortException(X_OTHER, "Invalid class %s in function call to %s. %s expected", check->GetClass()->TypeName.GetChars(), ActionFunc->PrintableName.GetChars(), cls->TypeName.GetChars());
+				}
+			};
+			
+			if (ActionFunc->ImplicitArgs >= 1)
+			{
+				auto argtypes = ActionFunc->Proto->ArgumentTypes;
+				
+				CheckType(self, argtypes[0]);
+				
+				if (ActionFunc->ImplicitArgs >= 2)
+				{
+					CheckType(stateowner, argtypes[1]);
+				}
+				
+			}
+			
+			
 			if (stateret == nullptr)
 			{
 				VMCall(ActionFunc, params, ActionFunc->ImplicitArgs, nullptr, 0);