diff --git a/src/p_mobj.cpp b/src/p_mobj.cpp
index 458ed36f0d..c1be116eea 100644
--- a/src/p_mobj.cpp
+++ b/src/p_mobj.cpp
@@ -3410,7 +3410,8 @@ void AActor::Tick ()
 		// won't hurt anything. Don't do this if damage is 0! That way, you can
 		// still have missiles that go straight up and down through actors without
 		// damaging anything.
-		if ((flags & MF_MISSILE) && (velx|vely) == 0 && Damage != 0)
+		// (for backwards compatibility this must check for lack of damage function, not for zero damage!)
+		if ((flags & MF_MISSILE) && (velx|vely) == 0 && Damage != NULL)
 		{
 			velx = 1;
 		}
diff --git a/src/thingdef/thingdef.cpp b/src/thingdef/thingdef.cpp
index d162a9f107..8a3589a997 100644
--- a/src/thingdef/thingdef.cpp
+++ b/src/thingdef/thingdef.cpp
@@ -446,11 +446,19 @@ void LoadActors ()
 
 VMScriptFunction *CreateDamageFunction(int dmg)
 {
-	VMFunctionBuilder build;
-	build.Registers[REGT_POINTER].Get(1);		// The self pointer
-	build.EmitRetInt(0, false, dmg);
-	build.EmitRetInt(1, true, 0);
-	VMScriptFunction *sfunc = build.MakeFunction();
-	sfunc->NumArgs = 1;
-	return sfunc;
+	if (dmg == 0)
+	{
+		// For zero damage, do not create a function so that the special collision detection case still works as before.
+		return NULL;
+	}
+	else
+	{
+		VMFunctionBuilder build;
+		build.Registers[REGT_POINTER].Get(1);		// The self pointer
+		build.EmitRetInt(0, false, dmg);
+		build.EmitRetInt(1, true, 0);
+		VMScriptFunction *sfunc = build.MakeFunction();
+		sfunc->NumArgs = 1;
+		return sfunc;
+	}
 }