diff --git a/src/p_acs.cpp b/src/p_acs.cpp
index 4eeec97351..ac06041ee6 100644
--- a/src/p_acs.cpp
+++ b/src/p_acs.cpp
@@ -4007,8 +4007,8 @@ int DLevelScript::RunScript ()
 	FRemapTable *translation = 0;
 	int resultValue = 1;
 
-	// Hexen truncates all special arguments to bytes.
-	const int specialargmask = (level.flags2 & LEVEL2_HEXENHACK) ? 255 : ~0;
+	// Hexen truncates all special arguments to bytes (only when using an old MAPINFO and old ACS format
+	const int specialargmask = ((level.flags2 & LEVEL2_HEXENHACK) && activeBehavior->GetFormat() == ACS_Old) ? 255 : ~0;
 
 	switch (state)
 	{