diff --git a/src/p_actionfunctions.cpp b/src/p_actionfunctions.cpp
index 13a347ef2..885bb050c 100644
--- a/src/p_actionfunctions.cpp
+++ b/src/p_actionfunctions.cpp
@@ -1454,10 +1454,11 @@ enum CM_Flags
 	CMF_OFFSETPITCH = 32,
 	CMF_SAVEPITCH = 64,
 
-	CMF_ABSOLUTEANGLE = 128
+	CMF_ABSOLUTEANGLE = 128,
+	CMF_BADPITCH = 256
 };
 
-DEFINE_ACTION_FUNCTION(AActor, A_CustomMissile)
+DEFINE_ACTION_FUNCTION(AActor, A_SpawnProjectile)
 {
 	PARAM_SELF_PROLOGUE(AActor);
 	PARAM_CLASS		(ti, AActor);
@@ -1525,6 +1526,7 @@ DEFINE_ACTION_FUNCTION(AActor, A_CustomMissile)
 					}
 					missilespeed = fabs(Pitch.Cos() * missile->Speed);
 					missile->Vel.Z = Pitch.Sin() * missile->Speed;
+					if (!(flags & CMF_BADPITCH)) missile->Vel.Z *= -1;
 				}
 				else
 				{
@@ -1831,7 +1833,7 @@ static void AimBulletMissile(AActor *proj, AActor *puff, int flags, bool temp, b
 			// Aim for the base of the puff as that's where blood puffs will spawn... roughly.
 
 			A_Face(proj, puff, 0., 0., 0., 0., 1);
-			proj->Vel3DFromAngle(-proj->Angles.Pitch, proj->Speed);
+			proj->Vel3DFromAngle(proj->Angles.Pitch, proj->Speed);
 
 			if (!temp)
 			{
diff --git a/src/p_mobj.cpp b/src/p_mobj.cpp
index b527bf681..72ddd9395 100644
--- a/src/p_mobj.cpp
+++ b/src/p_mobj.cpp
@@ -6321,7 +6321,7 @@ bool P_CheckMissileSpawn (AActor* th, double maxdist)
 		// [RH] Don't explode ripping missiles that spawn inside something
 		if (th->BlockingMobj == NULL || !(th->flags2 & MF2_RIP) || (th->BlockingMobj->flags5 & MF5_DONTRIP))
 		{
-			// If this is a monster spawned by A_CustomMissile subtract it from the counter.
+			// If this is a monster spawned by A_SpawnProjectile subtract it from the counter.
 			th->ClearCounters();
 			// [RH] Don't explode missiles that spawn on top of horizon lines
 			if (th->BlockingLine != NULL && th->BlockingLine->special == Line_Horizon)
diff --git a/wadsrc/static/zscript.txt b/wadsrc/static/zscript.txt
index 341fdc9fb..3cad69783 100644
--- a/wadsrc/static/zscript.txt
+++ b/wadsrc/static/zscript.txt
@@ -2,6 +2,7 @@
 #include "zscript/constants.txt"
 #include "zscript/actor.txt"
 #include "zscript/actor_checks.txt"
+#include "zscript/compatibility.txt"
 
 #include "zscript/shared/inventory.txt"
 #include "zscript/shared/inv_misc.txt"
diff --git a/wadsrc/static/zscript/actor.txt b/wadsrc/static/zscript/actor.txt
index 0d264580a..4324f162a 100644
--- a/wadsrc/static/zscript/actor.txt
+++ b/wadsrc/static/zscript/actor.txt
@@ -691,7 +691,7 @@ class Actor : Thinker native
 	deprecated native void A_StopSoundEx(name slot);
 	native void A_SeekerMissile(int threshold, int turnmax, int flags = 0, int chance = 50, int distance = 10);
 	native action state A_Jump(int chance, statelabel label, ...);
-	native void A_CustomMissile(class<Actor> missiletype, double spawnheight = 32, double spawnofs_xy = 0, double angle = 0, int flags = 0, double pitch = 0, int ptr = AAPTR_TARGET);
+	native void A_SpawnProjectile(class<Actor> missiletype, double spawnheight = 32, double spawnofs_xy = 0, double angle = 0, int flags = 0, double pitch = 0, int ptr = AAPTR_TARGET);
 	native void A_CustomBulletAttack(double spread_xy, double spread_z, int numbullets, int damageperbullet, class<Actor> pufftype = "BulletPuff", double range = 0, int flags = 0, int ptr = AAPTR_TARGET, class<Actor> missile = null, double Spawnheight = 32, double Spawnofs_xy = 0);
 	native void A_CustomRailgun(int damage, int spawnofs_xy = 0, color color1 = 0, color color2 = 0, int flags = 0, int aim = 0, double maxdiff = 0, class<Actor> pufftype = "BulletPuff", double spread_xy = 0, double spread_z = 0, double range = 0, int duration = 0, double sparsity = 1.0, double driftspeed = 1.0, class<Actor> spawnclass = null, double spawnofs_z = 0, int spiraloffset = 270, int limit = 0);
 	native bool A_SetInventory(class<Inventory> itemtype, int amount, int ptr = AAPTR_DEFAULT, bool beyondMax = false);
diff --git a/wadsrc/static/zscript/compatibility.txt b/wadsrc/static/zscript/compatibility.txt
new file mode 100644
index 000000000..771e3b44b
--- /dev/null
+++ b/wadsrc/static/zscript/compatibility.txt
@@ -0,0 +1,9 @@
+// This file contains compatibility wrappers for DECORATE functions with bad parameters.
+
+extend class Actor
+{
+	deprecated void A_CustomMissile(class<Actor> missiletype, double spawnheight = 32, double spawnofs_xy = 0, double angle = 0, int flags = 0, double pitch = 0, int ptr = AAPTR_TARGET)
+	{
+		A_SpawnProjectile(missiletype, spawnheight, spawnofs_xy, angle, flags|CMF_BADPITCH, pitch, ptr);
+	}
+}
\ No newline at end of file
diff --git a/wadsrc/static/zscript/constants.txt b/wadsrc/static/zscript/constants.txt
index 6f57b4222..1d2064aa1 100644
--- a/wadsrc/static/zscript/constants.txt
+++ b/wadsrc/static/zscript/constants.txt
@@ -45,7 +45,7 @@ enum EBFGSprayFlags
 	BFGF_MISSILEORIGIN = 2,
 };
 
-// Flags for A_CustomMissile
+// Flags for A_SpawnProjectile
 enum ECustomMissileFlags
 {
 	CMF_AIMOFFSET = 1,
@@ -56,6 +56,7 @@ enum ECustomMissileFlags
 	CMF_OFFSETPITCH = 32,
 	CMF_SAVEPITCH = 64,
 	CMF_ABSOLUTEANGLE = 128,
+	CMF_BADPITCH = 256,	// for compatibility handling only - avoid!
 };
 
 // Flags for A_CustomBulletAttack
diff --git a/wadsrc/static/zscript/heretic/snake.txt b/wadsrc/static/zscript/heretic/snake.txt
index 613559a86..15ae342aa 100644
--- a/wadsrc/static/zscript/heretic/snake.txt
+++ b/wadsrc/static/zscript/heretic/snake.txt
@@ -28,9 +28,9 @@ class Snake : Actor
 		Loop;
 	Missile:
 		SNKE FF 5 A_FaceTarget;
-		SNKE FFF 4 A_CustomMissile("SnakeProjA", 32, 0, 0, CMF_CHECKTARGETDEAD);
+		SNKE FFF 4 A_SpawnProjectile("SnakeProjA", 32, 0, 0, CMF_CHECKTARGETDEAD);
 		SNKE FFF 5 A_FaceTarget;
-		SNKE F 4 A_CustomMissile("SnakeProjB", 32, 0, 0, CMF_CHECKTARGETDEAD);
+		SNKE F 4 A_SpawnProjectile("SnakeProjB", 32, 0, 0, CMF_CHECKTARGETDEAD);
 		Goto See;
 	Pain:
 		SNKE E 3;
diff --git a/wadsrc/static/zscript/hexen/centaur.txt b/wadsrc/static/zscript/hexen/centaur.txt
index f8c8e2c3d..abf2f19d2 100644
--- a/wadsrc/static/zscript/hexen/centaur.txt
+++ b/wadsrc/static/zscript/hexen/centaur.txt
@@ -112,9 +112,9 @@ class CentaurLeader : Centaur
 	{
 	Missile:
 		CENT E 10 A_FaceTarget;
-		CENT F 8 Bright A_CustomMissile("CentaurFX", 45, 0, 0, CMF_AIMOFFSET);
+		CENT F 8 Bright A_SpawnProjectile("CentaurFX", 45, 0, 0, CMF_AIMOFFSET);
 		CENT E 10 A_FaceTarget;
-		CENT F 8 Bright A_CustomMissile("CentaurFX", 45, 0, 0, CMF_AIMOFFSET);
+		CENT F 8 Bright A_SpawnProjectile("CentaurFX", 45, 0, 0, CMF_AIMOFFSET);
 		Goto See;
 	}
 }		
diff --git a/wadsrc/static/zscript/hexen/demons.txt b/wadsrc/static/zscript/hexen/demons.txt
index 25e078509..ef4c96d8d 100644
--- a/wadsrc/static/zscript/hexen/demons.txt
+++ b/wadsrc/static/zscript/hexen/demons.txt
@@ -44,7 +44,7 @@ class Demon1 : Actor
 	Missile:
 		DEMN E 5 A_FaceTarget;
 		DEMN F 6 A_FaceTarget;
-		DEMN G 5 A_CustomMissile("Demon1FX1", 62, 0);
+		DEMN G 5 A_SpawnProjectile("Demon1FX1", 62, 0);
 		Goto See;
 	Death:
 		DEMN HI 6;
@@ -250,7 +250,7 @@ class Demon2 : Demon1
 	Missile:
 		DEM2 E 5 A_FaceTarget;
 		DEM2 F 6 A_FaceTarget;
-		DEM2 G 5 A_CustomMissile("Demon2FX1", 62, 0);
+		DEM2 G 5 A_SpawnProjectile("Demon2FX1", 62, 0);
 		Goto See;
 	Death:
 		DEM2 HI 6;
diff --git a/wadsrc/static/zscript/hexen/serpent.txt b/wadsrc/static/zscript/hexen/serpent.txt
index 6eaafcfd1..eb26c8c7b 100644
--- a/wadsrc/static/zscript/hexen/serpent.txt
+++ b/wadsrc/static/zscript/hexen/serpent.txt
@@ -300,7 +300,7 @@ class SerpentLeader : Serpent
 	States
 	{
 	Missile:
-		SSPT N 5 A_CustomMissile("SerpentFX", 32, 0);
+		SSPT N 5 A_SpawnProjectile("SerpentFX", 32, 0);
 		Goto Dive;
 	}
 }
diff --git a/wadsrc/static/zscript/hexen/wraith.txt b/wadsrc/static/zscript/hexen/wraith.txt
index 42a81ae6c..4b90dc4f6 100644
--- a/wadsrc/static/zscript/hexen/wraith.txt
+++ b/wadsrc/static/zscript/hexen/wraith.txt
@@ -47,7 +47,7 @@ class Wraith : Actor
 	Missile:
 		WRTH E 6 A_FaceTarget;
 		WRTH F 6;
-		WRTH G 6 A_CustomMissile("WraithFX1");
+		WRTH G 6 A_SpawnProjectile("WraithFX1");
 		Goto See;
 	Death:
 		WRTH I 4;
diff --git a/wadsrc/static/zscript/strife/alienspectres.txt b/wadsrc/static/zscript/strife/alienspectres.txt
index 39cbc8331..791266cc0 100644
--- a/wadsrc/static/zscript/strife/alienspectres.txt
+++ b/wadsrc/static/zscript/strife/alienspectres.txt
@@ -202,7 +202,7 @@ class AlienSpectre2 : AlienSpectre1
 	{
 	Missile:
 		ALN1 F 4 A_FaceTarget;
-		ALN1 I 4 A_CustomMissile("SpectralLightningH3", 32, 0);
+		ALN1 I 4 A_SpawnProjectile("SpectralLightningH3", 32, 0);
 		ALN1 E 4;
 		Goto See+10;
 	}
@@ -267,7 +267,7 @@ class AlienSpectre4 : AlienSpectre1
 	{
 	Missile:
 		ALN1 F 4 A_FaceTarget;
-		ALN1 I 4 A_CustomMissile("SpectralLightningBigV2", 32, 0);
+		ALN1 I 4 A_SpawnProjectile("SpectralLightningBigV2", 32, 0);
 		ALN1 E 4;
 		Goto See+10;
 	}
@@ -289,7 +289,7 @@ class AlienSpectre5 : AlienSpectre1
 	{
 	Missile:
 		ALN1 F 4 A_FaceTarget;
-		ALN1 I 4 A_CustomMissile("SpectralLightningBigBall2", 32, 0);
+		ALN1 I 4 A_SpawnProjectile("SpectralLightningBigBall2", 32, 0);
 		ALN1 E 4;
 		Goto See+10;
 	}
diff --git a/wadsrc/static/zscript/strife/entityboss.txt b/wadsrc/static/zscript/strife/entityboss.txt
index daf1a78ee..a9ec94bb2 100644
--- a/wadsrc/static/zscript/strife/entityboss.txt
+++ b/wadsrc/static/zscript/strife/entityboss.txt
@@ -265,7 +265,7 @@ class EntitySecond : SpectralMonster
 		Goto See+1;
 	Missile:
 		MNAL W 4 Bright A_FaceTarget;
-		MNAL U 4 Bright A_CustomMissile("SpectralLightningH3",32,0);
+		MNAL U 4 Bright A_SpawnProjectile("SpectralLightningH3",32,0);
 		MNAL V 4 Bright A_SentinelBob;
 		Goto See+4;
 	Pain:
diff --git a/wadsrc/static/zscript/strife/loremaster.txt b/wadsrc/static/zscript/strife/loremaster.txt
index 14571f91c..cda305d18 100644
--- a/wadsrc/static/zscript/strife/loremaster.txt
+++ b/wadsrc/static/zscript/strife/loremaster.txt
@@ -55,7 +55,7 @@ class Loremaster : Actor
 		Goto See;
 	Missile:
 		PRST E 4 A_FaceTarget;
-		PRST F 4 A_CustomMissile("LoreShot", 32, 0);
+		PRST F 4 A_SpawnProjectile("LoreShot", 32, 0);
 		PRST E 4 A_SentinelBob;
 		Goto See;
 	Death:
diff --git a/wadsrc/static/zscript/strife/strifebishop.txt b/wadsrc/static/zscript/strife/strifebishop.txt
index b7de186a2..32aacd03a 100644
--- a/wadsrc/static/zscript/strife/strifebishop.txt
+++ b/wadsrc/static/zscript/strife/strifebishop.txt
@@ -38,7 +38,7 @@ class StrifeBishop : Actor
 		Loop;
 	Missile:
 		MLDR E 3 A_FaceTarget;
-		MLDR F 2 Bright A_CustomMissile("BishopMissile", 64, 0, 0, CMF_AIMOFFSET);
+		MLDR F 2 Bright A_SpawnProjectile("BishopMissile", 64, 0, 0, CMF_AIMOFFSET);
 		Goto See;
 	Pain:
 		MLDR D 1 A_Pain;