diff --git a/source/games/duke/src/savegame.cpp b/source/games/duke/src/savegame.cpp
index 9f803d758..cbdf5130d 100644
--- a/source/games/duke/src/savegame.cpp
+++ b/source/games/duke/src/savegame.cpp
@@ -42,10 +42,10 @@ extern FixedBitArray<MAXSPRITES> activeSprites;
 
 template<> FSerializer& Serialize(FSerializer& arc, const char* key, Duke3d::weaponhit*& ht, Duke3d::weaponhit** def)
 {
-	size_t index = ht - Duke3d::hittype;
-	assert(index < MAXSPRITES);
+	ptrdiff_t index = ht? ht - Duke3d::hittype : -1;
+	assert(index >= -1 && index < MAXSPRITES);
 	Serialize(arc, key, index, nullptr);
-	ht = &Duke3d::hittype[index];
+	ht = index < 0? nullptr : &Duke3d::hittype[index];
 	return arc;
 }