diff --git a/src/actor.h b/src/actor.h
index 995c4d0732..970397d15d 100644
--- a/src/actor.h
+++ b/src/actor.h
@@ -797,7 +797,7 @@ public:
 	fixed_t			velx, vely, velz;	// velocity
 	SDWORD			tics;				// state tic counter
 	FState			*state;
-	SDWORD			Damage;			// For missiles and monster railgun
+	VMFunction		*Damage;			// For missiles and monster railgun
 	int				projectileKickback;
 	DWORD			flags;
 	DWORD			flags2;			// Heretic flags
diff --git a/src/d_dehacked.cpp b/src/d_dehacked.cpp
index 97f76bce64..c1e3b28000 100644
--- a/src/d_dehacked.cpp
+++ b/src/d_dehacked.cpp
@@ -852,7 +852,7 @@ static int PatchThing (int thingy)
 		}
 		else if (linelen == 14 && stricmp (Line1, "Missile damage") == 0)
 		{
-			info->Damage = val;
+			info->Damage = CreateDamageFunction(val);
 		}
 		else if (linelen == 5)
 		{
diff --git a/src/g_doom/a_bossbrain.cpp b/src/g_doom/a_bossbrain.cpp
index 59191032c2..51d7f0e624 100644
--- a/src/g_doom/a_bossbrain.cpp
+++ b/src/g_doom/a_bossbrain.cpp
@@ -47,7 +47,7 @@ static void BrainishExplosion (fixed_t x, fixed_t y, fixed_t z)
 				boom->SetState (state);
 		}
 		boom->effects = 0;
-		boom->Damage = 0;	// disables collision detection which is not wanted here
+		boom->Damage = NULL;	// disables collision detection which is not wanted here
 		boom->tics -= pr_brainscream() & 7;
 		if (boom->tics < 1)
 			boom->tics = 1;
diff --git a/src/g_doom/a_fatso.cpp b/src/g_doom/a_fatso.cpp
index 67ae803b9b..015e82916e 100644
--- a/src/g_doom/a_fatso.cpp
+++ b/src/g_doom/a_fatso.cpp
@@ -144,7 +144,7 @@ DEFINE_ACTION_FUNCTION_PARAMS(AActor, A_Mushroom)
 
 	if (n == 0)
 	{
-		n = self->Damage; // GetMissileDamage (0, 1);
+		n = self->GetMissileDamage(0, 1);
 	}
 	if (spawntype == NULL)
 	{
diff --git a/src/g_doom/a_lostsoul.cpp b/src/g_doom/a_lostsoul.cpp
index 887f2d9d79..a8fb44c0ae 100644
--- a/src/g_doom/a_lostsoul.cpp
+++ b/src/g_doom/a_lostsoul.cpp
@@ -65,7 +65,7 @@ DEFINE_ACTION_FUNCTION(AActor, A_BetaSkullAttack)
 		return 0;
 	S_Sound (self, CHAN_WEAPON, self->AttackSound, 1, ATTN_NORM);
 	A_FaceTarget(self);
-	damage = (pr_oldsoul()%8+1)*self->Damage;
+	damage = (pr_oldsoul()%8+1)*self->GetMissileDamage(0,1);
 	P_DamageMobj(self->target, self, self, damage, NAME_None);
 	return 0;
 }
diff --git a/src/g_heretic/a_ironlich.cpp b/src/g_heretic/a_ironlich.cpp
index 0a345d2a6f..852f3d2582 100644
--- a/src/g_heretic/a_ironlich.cpp
+++ b/src/g_heretic/a_ironlich.cpp
@@ -116,7 +116,7 @@ DEFINE_ACTION_FUNCTION(AActor, A_LichAttack)
 				fire->velx = baseFire->velx;
 				fire->vely = baseFire->vely;
 				fire->velz = baseFire->velz;
-				fire->Damage = 0;
+				fire->Damage = NULL;
 				fire->health = (i+1) * 2;
 				P_CheckMissileSpawn (fire);
 			}
diff --git a/src/g_hexen/a_magelightning.cpp b/src/g_hexen/a_magelightning.cpp
index 7010aaceb0..0a31ef1433 100644
--- a/src/g_hexen/a_magelightning.cpp
+++ b/src/g_hexen/a_magelightning.cpp
@@ -356,7 +356,7 @@ DEFINE_ACTION_FUNCTION(AActor, A_LastZap)
 	{
 		mo->SetState (mo->FindState (NAME_Death));
 		mo->velz = 40*FRACUNIT;
-		mo->Damage = 0;
+		mo->Damage = NULL;
 	}
 	return 0;
 }
diff --git a/src/info.cpp b/src/info.cpp
index 361ba4bf02..523855084d 100644
--- a/src/info.cpp
+++ b/src/info.cpp
@@ -302,6 +302,9 @@ size_t PClassActor::PropagateMark()
 			GC::Mark(OwnedStates[i].ActionFunc);
 		}
 	}
+	// Mark damage function
+	GC::Mark(((AActor *)Defaults)->Damage);
+
 //	marked += ActorInfo->NumOwnedStates * sizeof(FState);
 	return Super::PropagateMark();
 }
diff --git a/src/p_acs.cpp b/src/p_acs.cpp
index 668c4dc1b1..81da86259c 100644
--- a/src/p_acs.cpp
+++ b/src/p_acs.cpp
@@ -2832,7 +2832,7 @@ void DLevelScript::DoSetActorProperty (AActor *actor, int property, int value)
 		break;
 
 	case APROP_Damage:
-		actor->Damage = value;
+		actor->Damage = CreateDamageFunction(value);
 		break;
 
 	case APROP_Alpha:
@@ -2994,7 +2994,7 @@ int DLevelScript::GetActorProperty (int tid, int property)
 	{
 	case APROP_Health:		return actor->health;
 	case APROP_Speed:		return actor->Speed;
-	case APROP_Damage:		return actor->Damage;	// Should this call GetMissileDamage() instead?
+	case APROP_Damage:		return actor->GetMissileDamage(0,1);
 	case APROP_DamageFactor:return actor->DamageFactor;
 	case APROP_Alpha:		return actor->alpha;
 	case APROP_RenderStyle:	for (int style = STYLE_None; style < STYLE_Count; ++style)
diff --git a/src/p_mobj.cpp b/src/p_mobj.cpp
index f0fcf9b467..458ed36f0d 100644
--- a/src/p_mobj.cpp
+++ b/src/p_mobj.cpp
@@ -136,6 +136,7 @@ IMPLEMENT_POINTY_CLASS (AActor)
  DECLARE_POINTER (LastHeard)
  DECLARE_POINTER (master)
  DECLARE_POINTER (Poisoner)
+ DECLARE_POINTER (Damage)
 END_POINTERS
 
 AActor::~AActor ()
@@ -2778,21 +2779,34 @@ CCMD(utid)
 
 int AActor::GetMissileDamage (int mask, int add)
 {
-	if ((Damage & 0xC0000000) == 0x40000000)
-	{
-		return EvalExpressionI (Damage & 0x3FFFFFFF, this);
-	}
-	if (Damage == 0)
+	if (Damage == NULL)
 	{
 		return 0;
 	}
+	VMFrameStack stack;
+	VMValue param = this;
+	VMReturn results[2];
+
+	int amount, calculated = false;
+
+	results[0].IntAt(&amount);
+	results[1].IntAt(&calculated);
+
+	if (stack.Call(Damage, &param, 1, results, 2) < 1)
+	{ // No results
+		return 0;
+	}
+	if (calculated)
+	{
+		return amount;
+	}
 	else if (mask == 0)
 	{
-		return add * Damage;
+		return add * amount;
 	}
 	else
 	{
-		return ((pr_missiledamage() & mask) + add) * Damage;
+		return ((pr_missiledamage() & mask) + add) * amount;
 	}
 }
 
diff --git a/src/thingdef/olddecorations.cpp b/src/thingdef/olddecorations.cpp
index 78d890be07..8c1da024c1 100644
--- a/src/thingdef/olddecorations.cpp
+++ b/src/thingdef/olddecorations.cpp
@@ -495,7 +495,7 @@ static void ParseInsideDecoration (Baggage &bag, AActor *defaults,
 		else if (def == DEF_Projectile && sc.Compare ("Damage"))
 		{
 			sc.MustGetNumber ();
-			defaults->Damage = sc.Number;
+			defaults->Damage = CreateDamageFunction(sc.Number);
 		}
 		else if (def == DEF_Projectile && sc.Compare ("DamageType"))
 		{
diff --git a/src/thingdef/thingdef.cpp b/src/thingdef/thingdef.cpp
index b764e48abd..d162a9f107 100644
--- a/src/thingdef/thingdef.cpp
+++ b/src/thingdef/thingdef.cpp
@@ -261,6 +261,17 @@ void FinishActor(const FScriptPosition &sc, PClassActor *info, Baggage &bag)
 //
 //==========================================================================
 
+static void DumpFunction(FILE *dump, VMScriptFunction *sfunc, const char *label, int labellen)
+{
+	const char *marks = "=======================================================";
+	fprintf(dump, "\n%.*s %s %.*s", MAX(3, 38 - labellen / 2), marks, label, MAX(3, 38 - labellen / 2), marks);
+	fprintf(dump, "\nInteger regs: %-3d  Float regs: %-3d  Address regs: %-3d  String regs: %-3d\nStack size: %d\n",
+		sfunc->NumRegD, sfunc->NumRegF, sfunc->NumRegA, sfunc->NumRegS, sfunc->MaxParam);
+	VMDumpConstants(dump, sfunc);
+	fprintf(dump, "\nDisassembly @ %p:\n", sfunc->Code);
+	VMDisasm(dump, sfunc->Code, sfunc->CodeSize, sfunc);
+}
+
 static void FinishThingdef()
 {
 	int errorcount = StateParams.ResolveAll();
@@ -305,17 +316,10 @@ static void FinishThingdef()
 			sfunc->NumArgs = NAP;
 			func = sfunc;
 #if 1
-			const char *marks = "=======================================================";
 			char label[64];
 			int labellen = mysnprintf(label, countof(label), "Function %s.States[%d] (*%d)",
-				tcall->ActorClass->TypeName.GetChars(),
-				tcall->FirstState, tcall->NumStates);
-			fprintf(dump, "\n%.*s %s %.*s", MAX(3, 38 - labellen / 2), marks, label, MAX(3, 38 - labellen / 2), marks);
-			fprintf(dump, "\nInteger regs: %-3d  Float regs: %-3d  Address regs: %-3d  String regs: %-3d\nStack size: %d\n",
-				sfunc->NumRegD, sfunc->NumRegF, sfunc->NumRegA, sfunc->NumRegS, sfunc->MaxParam);
-			VMDumpConstants(dump, sfunc);
-			fprintf(dump, "\nDisassembly @ %p:\n", sfunc->Code);
-			VMDisasm(dump, sfunc->Code, sfunc->CodeSize, sfunc);
+				tcall->ActorClass->TypeName.GetChars(), tcall->FirstState, tcall->NumStates);
+			DumpFunction(dump, sfunc, label, labellen);
 			codesize += sfunc->CodeSize;
 #endif
 		}
@@ -324,10 +328,6 @@ static void FinishThingdef()
 			tcall->ActorClass->OwnedStates[tcall->FirstState + k].SetAction(func);
 		}
 	}
-#if 1
-	fprintf(dump, "\n*************************************************************************\n%i code bytes\n", codesize * 4);
-#endif
-	fclose(dump);
 
 	for (i = 0; i < PClassActor::AllActorClasses.Size(); i++)
 	{
@@ -348,7 +348,42 @@ static void FinishThingdef()
 			errorcount++;
 			continue;
 		}
+
+		if (def->Damage != NULL)
+		{
+			VMScriptFunction *sfunc;
+			FxDamageValue *dmg = (FxDamageValue *)def->Damage;
+			sfunc = dmg->GetFunction();
+			if (sfunc == NULL)
+			{
+				FCompileContext ctx(ti, true);
+				dmg->Resolve(ctx);
+				VMFunctionBuilder buildit;
+				buildit.Registers[REGT_POINTER].Get(1);		// The self pointer
+				dmg->Emit(&buildit);
+				sfunc = buildit.MakeFunction();
+				sfunc->NumArgs = 1;
+				// Save this function in case this damage value was reused
+				// (which happens quite easily with inheritance).
+				dmg->SetFunction(sfunc);
+			}
+			def->Damage = sfunc;
+#if 1
+			if (sfunc != NULL)
+			{
+				char label[64];
+				int labellen = mysnprintf(label, countof(label), "Function %s.Damage",
+					ti->TypeName.GetChars());
+				DumpFunction(dump, sfunc, label, labellen);
+				codesize += sfunc->CodeSize;
+			}
+#endif
+		}
 	}
+#if 1
+	fprintf(dump, "\n*************************************************************************\n%i code bytes\n", codesize * 4);
+#endif
+	fclose(dump);
 	if (errorcount > 0)
 	{
 		I_Error("%d errors during actor postprocessing", errorcount);
@@ -399,3 +434,23 @@ void LoadActors ()
 	// Base time: ~52 ms
 }
 
+
+//==========================================================================
+//
+// CreateDamageFunction
+//
+// Creates a damage function suitable for a constant, non-expressioned
+// value.
+//
+//==========================================================================
+
+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;
+}
diff --git a/src/thingdef/thingdef.h b/src/thingdef/thingdef.h
index 68d16e8fc1..2eb84b0024 100644
--- a/src/thingdef/thingdef.h
+++ b/src/thingdef/thingdef.h
@@ -141,8 +141,8 @@ public:
 	void Clear();
 	int Add(FxExpression *x, PClassActor *o, bool c);
 	int Reserve(int num, PClassActor *cls);
-	void Set(int num, FxExpression *x, bool cloned = false);
-	void Copy(int dest, int src, int cnt);
+//	void Set(int num, FxExpression *x, bool cloned = false);
+//	void Copy(int dest, int src, int cnt);
 	int ResolveAll();
 	FxExpression *Get(int no);
 	unsigned int Size() { return expressions.Size(); }
@@ -184,6 +184,14 @@ inline void ResetBaggage (Baggage *bag, PClassActor *stateclass)
 	bag->statedef.MakeStateDefines(stateclass);
 }
 
+//==========================================================================
+//
+// Damage function creation
+//
+//==========================================================================
+
+VMScriptFunction *CreateDamageFunction(int dmg);
+
 //==========================================================================
 //
 // Action function lookup
@@ -270,6 +278,7 @@ union FPropParam
 	int i;
 	float f;
 	const char *s;
+	FxExpression *exp;
 };
 
 typedef void (*PropHandler)(AActor *defaults, PClassActor *info, Baggage &bag, FPropParam *params);
@@ -328,6 +337,9 @@ int MatchString (const char *in, const char **strings);
 #define PROP_STRING_PARM(var, no) \
 	const char *var = params[(no)+1].s;
 
+#define PROP_EXP_PARM(var, no) \
+	FxExpression *var = params[(no)+1].exp;
+
 #define PROP_INT_PARM(var, no) \
 	int var = params[(no)+1].i;
 
@@ -375,44 +387,6 @@ int MatchString (const char *in, const char **strings);
 	}
 
 
-int EvalExpressionI (DWORD x, AActor *self);
-int EvalExpressionCol (DWORD x, AActor *self);
-FSoundID EvalExpressionSnd (DWORD x, AActor *self);
-double EvalExpressionF (DWORD x, AActor *self);
-fixed_t EvalExpressionFix (DWORD x, AActor *self);
-FState *EvalExpressionState (DWORD x, AActor *self);
-const PClass *EvalExpressionClass (DWORD x, AActor *self);
-FName EvalExpressionName (DWORD x, AActor *self);
-
-#if 0
-#define ACTION_PARAM_START(count)
-
-#define ACTION_PARAM_INT(var, i) \
-	int var = EvalExpressionI(ParameterIndex+i, self);
-#define ACTION_PARAM_BOOL(var,i) \
-	bool var = !!EvalExpressionI(ParameterIndex+i, self);
-#define ACTION_PARAM_FIXED(var,i) \
-	fixed_t var = EvalExpressionFix(ParameterIndex+i, self);
-#define ACTION_PARAM_FLOAT(var,i) \
-	float var = float(EvalExpressionF(ParameterIndex+i, self));
-#define ACTION_PARAM_DOUBLE(var,i) \
-	double var = EvalExpressionF(ParameterIndex+i, self);
-#define ACTION_PARAM_CLASS(var,i) \
-	const PClass *var = EvalExpressionClass(ParameterIndex+i, self);
-#define ACTION_PARAM_STATE(var,i) \
-	FState *var = EvalExpressionState(ParameterIndex+i, stateowner);
-#define ACTION_PARAM_COLOR(var,i) \
-	PalEntry var = EvalExpressionCol(ParameterIndex+i, self);
-#define ACTION_PARAM_SOUND(var,i) \
-	FSoundID var = EvalExpressionSnd(ParameterIndex+i, self);
-#define ACTION_PARAM_STRING(var,i) \
-	const char *var = EvalExpressionName(ParameterIndex+i, self);
-#define ACTION_PARAM_NAME(var,i) \
-	FName var = EvalExpressionName(ParameterIndex+i, self);
-#define ACTION_PARAM_ANGLE(var,i) \
-	angle_t var = angle_t(EvalExpressionF(ParameterIndex+i, self)*ANGLE_90/90.f);
-#endif
-
 #define ACTION_SET_RESULT(v) do { if (numret > 0) { assert(ret != NULL); ret->SetInt(v); numret = 1; } } while(0)
 
 // Checks to see what called the current action function
diff --git a/src/thingdef/thingdef_exp.h b/src/thingdef/thingdef_exp.h
index ccf73eb346..abca3c722c 100644
--- a/src/thingdef/thingdef_exp.h
+++ b/src/thingdef/thingdef_exp.h
@@ -904,6 +904,28 @@ public:
 	ExpEmit Emit(VMFunctionBuilder *build);
 };
 
+//==========================================================================
+//
+//
+//
+//==========================================================================
+
+class FxDamageValue : public FxExpression
+{
+	FxExpression *val;
+	bool Calculated;
+	VMScriptFunction *MyFunction;
+
+public:
+
+	FxDamageValue(FxExpression *v, bool calc);
+	~FxDamageValue();
+	FxExpression *Resolve(FCompileContext&);
+
+	ExpEmit Emit(VMFunctionBuilder *build);
+	VMScriptFunction *GetFunction() const { return MyFunction; }
+	void SetFunction(VMScriptFunction *func) { MyFunction = func; }
+};
 
 
 FxExpression *ParseExpression (FScanner &sc, PClassActor *cls);
diff --git a/src/thingdef/thingdef_expression.cpp b/src/thingdef/thingdef_expression.cpp
index ea5c5005e5..7c68d99b5e 100644
--- a/src/thingdef/thingdef_expression.cpp
+++ b/src/thingdef/thingdef_expression.cpp
@@ -79,7 +79,7 @@ DEFINE_MEMBER_VARIABLE_ALIAS(momy, vely, AActor)
 DEFINE_MEMBER_VARIABLE_ALIAS(momz, velz, AActor)
 DEFINE_MEMBER_VARIABLE(scaleX, AActor)
 DEFINE_MEMBER_VARIABLE(scaleY, AActor)
-DEFINE_MEMBER_VARIABLE(Damage, AActor)
+//DEFINE_MEMBER_VARIABLE(Damage, AActor)
 DEFINE_MEMBER_VARIABLE(Score, AActor)
 DEFINE_MEMBER_VARIABLE(accuracy, AActor)
 DEFINE_MEMBER_VARIABLE(stamina, AActor)
@@ -120,89 +120,6 @@ static PSymbol *FindDecorateBuiltinFunction(FName funcname, VMNativeFunction::Na
 	return sym;
 }
 
-//==========================================================================
-//
-// EvalExpression
-// [GRB] Evaluates previously stored expression
-//
-//==========================================================================
-
-
-int EvalExpressionI (DWORD xi, AActor *self)
-{
-	FxExpression *x = StateParams.Get(xi);
-	if (x == NULL) return 0;
-
-	return x->EvalExpression (self).GetInt();
-}
-
-int EvalExpressionCol (DWORD xi, AActor *self)
-{
-	FxExpression *x = StateParams.Get(xi);
-	if (x == NULL) return 0;
-
-	return x->EvalExpression (self).GetColor();
-}
-
-FSoundID EvalExpressionSnd (DWORD xi, AActor *self)
-{
-	FxExpression *x = StateParams.Get(xi);
-	if (x == NULL) return 0;
-
-	return x->EvalExpression (self).GetSoundID();
-}
-
-double EvalExpressionF (DWORD xi, AActor *self)
-{
-	FxExpression *x = StateParams.Get(xi);
-	if (x == NULL) return 0;
-
-	return x->EvalExpression (self).GetFloat();
-}
-
-fixed_t EvalExpressionFix (DWORD xi, AActor *self)
-{
-	FxExpression *x = StateParams.Get(xi);
-	if (x == NULL) return 0;
-
-	ExpVal val = x->EvalExpression (self);
-
-	switch (val.Type)
-	{
-	default:
-		return 0;
-	case VAL_Int:
-		return val.Int << FRACBITS;
-	case VAL_Float:
-		return fixed_t(val.Float*FRACUNIT);
-	}
-}
-
-FName EvalExpressionName (DWORD xi, AActor *self)
-{
-	FxExpression *x = StateParams.Get(xi);
-	if (x == NULL) return 0;
-
-	return x->EvalExpression (self).GetName();
-}
-
-const PClass * EvalExpressionClass (DWORD xi, AActor *self)
-{
-	FxExpression *x = StateParams.Get(xi);
-	if (x == NULL) return 0;
-
-	return x->EvalExpression (self).GetClass();
-}
-
-FState *EvalExpressionState (DWORD xi, AActor *self)
-{
-	FxExpression *x = StateParams.Get(xi);
-	if (x == NULL) return 0;
-
-	return x->EvalExpression (self).GetState();
-}
-
-
 //==========================================================================
 //
 //
@@ -4025,6 +3942,64 @@ ExpEmit FxMultiNameState::Emit(VMFunctionBuilder *build)
 	return dest;
 }
 
+//==========================================================================
+//
+//
+//
+//==========================================================================
+
+FxDamageValue::FxDamageValue(FxExpression *v, bool calc)
+: FxExpression(v->ScriptPosition)
+{
+	val = v;
+	ValueType = VAL_Unknown;
+	Calculated = calc;
+	MyFunction = NULL;
+
+	if (!calc)
+	{
+		assert(v->isConstant() && "Non-calculated damage must be constant");
+	}
+}
+
+FxDamageValue::~FxDamageValue()
+{
+	SAFE_DELETE(val);
+
+}
+
+FxExpression *FxDamageValue::Resolve(FCompileContext &ctx)
+{
+	CHECKRESOLVED();
+	SAFE_RESOLVE(val, ctx)
+
+	if (!val->ValueType.isNumeric())
+	{
+		ScriptPosition.Message(MSG_ERROR, "Numeric type expected");
+		delete this;
+		return NULL;
+	}
+	return this;
+}
+
+// This is a highly-specialized "expression" type that emits a complete function.
+ExpEmit FxDamageValue::Emit(VMFunctionBuilder *build)
+{
+	if (val->isConstant())
+	{
+		build->EmitRetInt(0, false, val->EvalExpression(NULL).Int);
+	}
+	else
+	{
+		ExpEmit emitval = val->Emit(build);
+		assert(emitval.RegType == REGT_INT);
+		build->Emit(OP_RET, 0, REGT_INT | (emitval.Konst ? REGT_KONST : 0), emitval.RegNum);
+	}
+	build->Emit(OP_RETI, 1, 0x8000 | (int)Calculated);
+
+	return ExpEmit();
+}
+
 
 //==========================================================================
 //
@@ -4096,38 +4071,6 @@ int FStateExpressions::Reserve(int num, PClassActor *cls)
 //
 //==========================================================================
 
-void FStateExpressions::Set(int num, FxExpression *x, bool cloned)
-{
-	if (num >= 0 && num < int(Size()))
-	{
-		assert(expressions[num].expr == NULL || expressions[num].cloned);
-		expressions[num].expr = x;
-		expressions[num].cloned = cloned;
-	}
-}
-
-//==========================================================================
-//
-//
-//
-//==========================================================================
-
-void FStateExpressions::Copy(int dest, int src, int cnt)
-{
-	for(int i=0; i<cnt; i++)
-	{
-		// For now set only a reference because these expressions may change when being resolved
-		expressions[dest+i].expr = (FxExpression*)intptr_t(src+i);
-		expressions[dest+i].cloned = true;
-	}
-}
-
-//==========================================================================
-//
-//
-//
-//==========================================================================
-
 int FStateExpressions::ResolveAll()
 {
 	int errorcount = 0;
diff --git a/src/thingdef/thingdef_parse.cpp b/src/thingdef/thingdef_parse.cpp
index 8b974ac8de..c9fb01911a 100644
--- a/src/thingdef/thingdef_parse.cpp
+++ b/src/thingdef/thingdef_parse.cpp
@@ -669,16 +669,26 @@ static bool ParsePropertyParams(FScanner &sc, FPropertyInfo *prop, AActor *defau
 			switch ((*p) & 223)
 			{
 			case 'X':	// Expression in parentheses or number.
-				
-				if (sc.CheckString ("("))
 				{
-					FxExpression *x = ParseExpression(sc, bag.Info);
-					conv.i = 0x40000000 | StateParams.Add(x, bag.Info, false);
+					FxExpression *x = NULL;
+
+					if (sc.CheckString ("("))
+					{
+						x = new FxDamageValue(new FxIntCast(ParseExpression(sc, bag.Info)), true);
+						sc.MustGetStringName(")");
+					}
+					else
+					{
+						sc.MustGetNumber();
+						if (sc.Number != 0)
+						{
+							x = new FxDamageValue(new FxConstant(sc.Number, bag.ScriptPosition), false);
+						}
+					}
+					conv.exp = x;
 					params.Push(conv);
-					sc.MustGetStringName(")");
-					break;
 				}
-				// fall through
+				break;
 
 			case 'I':
 				sc.MustGetNumber();
diff --git a/src/thingdef/thingdef_properties.cpp b/src/thingdef/thingdef_properties.cpp
index 576aa72b10..0d115ec5bb 100644
--- a/src/thingdef/thingdef_properties.cpp
+++ b/src/thingdef/thingdef_properties.cpp
@@ -449,7 +449,7 @@ DEFINE_PROPERTY(painthreshold, I, Actor)
 //==========================================================================
 DEFINE_PROPERTY(damage, X, Actor)
 {
-	PROP_INT_PARM(id, 0);
+	PROP_EXP_PARM(id, 0);
 
 	// Damage can either be a single number, in which case it is subject
 	// to the original damage calculation rules. Or, it can be an expression
@@ -457,7 +457,9 @@ DEFINE_PROPERTY(damage, X, Actor)
 	// compatibility reasons, expressions must be enclosed within
 	// parentheses.
 
-	defaults->Damage = id;
+	// Store this expression here for now. It will be converted to a function
+	// later once all actors have been processed.
+	defaults->Damage = (VMFunction *)id;
 }
 
 //==========================================================================
diff --git a/src/zscript/vmbuilder.cpp b/src/zscript/vmbuilder.cpp
index 4cf613d8f3..78051d8160 100644
--- a/src/zscript/vmbuilder.cpp
+++ b/src/zscript/vmbuilder.cpp
@@ -490,6 +490,27 @@ size_t VMFunctionBuilder::EmitLoadInt(int regnum, int value)
 	}
 }
 
+//==========================================================================
+//
+// VMFunctionBuilder :: EmitRetInt
+//
+// Returns an integer, using either an immediate value or a constant
+// register, as appropriate.
+//
+//==========================================================================
+
+size_t VMFunctionBuilder::EmitRetInt(int retnum, bool final, int value)
+{
+	if (value >= -16384 && value <= 16383)
+	{
+		return Emit(OP_RETI, retnum, value | (final << 15));
+	}
+	else
+	{
+		return Emit(OP_RETI, retnum, REGT_INT | REGT_KONST | (final ? REGT_FINAL : 0), GetConstantInt(value));
+	}
+}
+
 //==========================================================================
 //
 // VMFunctionBuilder :: Backpatch
diff --git a/src/zscript/vmbuilder.h b/src/zscript/vmbuilder.h
index 2399411f63..7587d1b207 100644
--- a/src/zscript/vmbuilder.h
+++ b/src/zscript/vmbuilder.h
@@ -37,6 +37,7 @@ public:
 	size_t Emit(int opcode, int opa, VM_SHALF opbc);
 	size_t Emit(int opcode, int opabc);
 	size_t EmitLoadInt(int regnum, int value);
+	size_t EmitRetInt(int retnum, bool final, int value);
 
 	void Backpatch(size_t addr, size_t target);
 	void BackpatchToHere(size_t addr);
diff --git a/src/zscript/vmdisasm.cpp b/src/zscript/vmdisasm.cpp
index 81eb50bbac..77abf9d12e 100644
--- a/src/zscript/vmdisasm.cpp
+++ b/src/zscript/vmdisasm.cpp
@@ -43,6 +43,7 @@
 #define RII16	MODE_AI | MODE_BCJOINT | MODE_BCIMMS
 #define I24		MODE_ABCJOINT
 #define I8		MODE_AIMMZ | MODE_BUNUSED | MODE_CUNUSED
+#define I8I16	MODE_AIMMZ | MODE_BCIMMZ
 #define __BCP	MODE_AUNUSED | MODE_BCJOINT | MODE_BCPARAM
 #define RPI8	MODE_AP | MODE_BIMMZ | MODE_CUNUSED
 #define KPI8	MODE_AKP | MODE_BIMMZ | MODE_CUNUSED
@@ -246,6 +247,22 @@ void VMDisasm(FILE *out, const VMOP *code, int codesize, const VMScriptFunction
 			}
 			break;
 
+		case OP_RETI:
+			if (a == 0 && code[i].i16 & 0x8000)
+			{
+				col = printf_wrapper(out, "%d", (code[i].i16 << 17) >> 17);
+			}
+			else
+			{
+				col = print_reg(out, 0, a, (mode & MODE_ATYPE) >> MODE_ASHIFT, 24, func);
+				col += print_reg(out, col, (code[i].i16 << 17) >> 17, MODE_IMMS, 16, func);
+				if (code[i].i16 & 0x8000)
+				{
+					col += printf_wrapper(out, " [final]");
+				}
+			}
+			break;
+
 		default:
 			if ((mode & MODE_BCTYPE) == MODE_BCCAST)
 			{
diff --git a/src/zscript/vmexec.h b/src/zscript/vmexec.h
index ff9b471d58..a1a22a964e 100644
--- a/src/zscript/vmexec.h
+++ b/src/zscript/vmexec.h
@@ -593,6 +593,18 @@ begin:
 			return a < numret ? a + 1 : numret;
 		}
 		NEXTOP;
+	OP(RETI):
+		assert(ret != NULL || numret == 0);
+		if (a < numret)
+		{
+			// Shifting by 17 to wipe out the final bit
+			ret[a].SetInt(((pc[-1].i16) << 17) >> 17);
+		}
+		if (pc[-1].i16 & 0x8000)
+		{
+			return a < numret ? a + 1 : numret;
+		}
+		NEXTOP;
 	OP(RESULT):
 		// This instruction is just a placeholder to indicate where a return
 		// value should be stored. It does nothing on its own and should not
diff --git a/src/zscript/vmops.h b/src/zscript/vmops.h
index 78ef5116f3..353dc3e85b 100644
--- a/src/zscript/vmops.h
+++ b/src/zscript/vmops.h
@@ -81,6 +81,7 @@ xx(TAIL,	tail,	RPI8),		// Call+Ret in a single instruction
 xx(TAIL_K,	tail,	KPI8),
 xx(RESULT,	result,	__BCP),		// Result should go in register encoded in BC (in caller, after CALL)
 xx(RET,		ret,	I8BCP),		// Copy value from register encoded in BC to return value A, possibly returning
+xx(RETI,	reti,	I8I16),		// Copy immediate from BC to return value A, possibly returning
 xx(TRY,		try,	I24),		// When an exception is thrown, start searching for a handler at pc + ABC
 xx(UNTRY,	untry,	I8),		// Pop A entries off the exception stack
 xx(THROW,	throw,	THROW),		// A == 0: Throw exception object pB
diff --git a/wadsrc/static/actors/actor.txt b/wadsrc/static/actors/actor.txt
index a6c7bd1c51..1f50643da8 100644
--- a/wadsrc/static/actors/actor.txt
+++ b/wadsrc/static/actors/actor.txt
@@ -41,7 +41,7 @@ ACTOR Actor native //: Thinker
 	native int tid;
 	native int TIDtoHate;
 	native int waterlevel;
-	native int damage;
+	//native int damage;
 	native fixed_t x;
 	native fixed_t y;
 	native fixed_t z;