diff --git a/src/g_game.cpp b/src/g_game.cpp
index 34b98c6073..8555db2c49 100644
--- a/src/g_game.cpp
+++ b/src/g_game.cpp
@@ -1230,7 +1230,7 @@ void G_PlayerFinishLevel (int player, EFinishLevelType mode, bool resetinventory
 
 	if (p->morphTics)
 	{ // Undo morph
-		P_UndoPlayerMorph (p, p, true);
+		P_UndoPlayerMorph (p, p, 0, true);
 	}
 
 	// Clears the entire inventory and gives back the defaults for starting a game
diff --git a/src/g_heretic/a_hereticartifacts.cpp b/src/g_heretic/a_hereticartifacts.cpp
index d9c08ec1a4..1b7a799660 100644
--- a/src/g_heretic/a_hereticartifacts.cpp
+++ b/src/g_heretic/a_hereticartifacts.cpp
@@ -24,7 +24,7 @@ bool AArtiTomeOfPower::Use (bool pickup)
 {
 	if (Owner->player->morphTics && (Owner->player->MorphStyle & MORPH_UNDOBYTOMEOFPOWER))
 	{ // Attempt to undo chicken
-		if (!P_UndoPlayerMorph (Owner->player, Owner->player))
+		if (!P_UndoPlayerMorph (Owner->player, Owner->player, MORPH_UNDOBYTOMEOFPOWER))
 		{ // Failed
 			if (!(Owner->player->MorphStyle & MORPH_FAILNOTELEFRAG))
 			{
diff --git a/src/g_raven/a_artitele.cpp b/src/g_raven/a_artitele.cpp
index 11350338ed..9828f95817 100644
--- a/src/g_raven/a_artitele.cpp
+++ b/src/g_raven/a_artitele.cpp
@@ -45,7 +45,8 @@ bool AArtiTeleport::Use (bool pickup)
 	bool canlaugh = true;
  	if (Owner->player->morphTics && (Owner->player->MorphStyle & MORPH_UNDOBYCHAOSDEVICE))
  	{ // Teleporting away will undo any morph effects (pig)
-		if (!P_UndoPlayerMorph (Owner->player, Owner->player) && (Owner->player->MorphStyle & MORPH_FAILNOLAUGH))
+		if (!P_UndoPlayerMorph (Owner->player, Owner->player, MORPH_UNDOBYCHAOSDEVICE)
+			&& (Owner->player->MorphStyle & MORPH_FAILNOLAUGH))
 		{
 			canlaugh = false;
 		}
diff --git a/src/g_shared/a_morph.cpp b/src/g_shared/a_morph.cpp
index 9ebec54ca4..f12c36aef0 100644
--- a/src/g_shared/a_morph.cpp
+++ b/src/g_shared/a_morph.cpp
@@ -173,7 +173,7 @@ bool P_MorphPlayer (player_t *activator, player_t *p, const PClass *spawntype, i
 //
 //----------------------------------------------------------------------------
 
-bool P_UndoPlayerMorph (player_t *activator, player_t *player, bool force)
+bool P_UndoPlayerMorph (player_t *activator, player_t *player, int unmorphflag, bool force)
 {
 	AWeapon *beastweap;
 	APlayerPawn *mo;
@@ -192,10 +192,12 @@ bool P_UndoPlayerMorph (player_t *activator, player_t *player, bool force)
 		return false;
 	}
 
-	if ((pmo->flags2 & MF2_INVULNERABLE) // If the player is invulnerable
-		&& ((player != activator)		// and either did not decide to unmorph,
-		|| (!((player->MorphStyle & MORPH_WHENINVULNERABLE)  // or the morph style does not allow it
-		&& (player->MorphStyle != MORPH_OLDEFFECTS))))) // (but standard morph styles always allow it),
+	bool DeliberateUnmorphIsOkay = !!(player->MorphStyle & unmorphflag);
+
+    if ((pmo->flags2 & MF2_INVULNERABLE) // If the player is invulnerable
+        && ((player != activator)       // and either did not decide to unmorph,
+        || (!((player->MorphStyle & MORPH_WHENINVULNERABLE)  // or the morph style does not allow it
+        || (DeliberateUnmorphIsOkay))))) // (but standard morph styles always allow it),
 	{ // Then the player is immune to the unmorph.
 		return false;
 	}
diff --git a/src/g_shared/a_morph.h b/src/g_shared/a_morph.h
index 7ae83aed45..1ddbf863d5 100644
--- a/src/g_shared/a_morph.h
+++ b/src/g_shared/a_morph.h
@@ -17,7 +17,7 @@ enum
 	MORPH_UNDOBYCHAOSDEVICE	= 0x00000008,	// Player unmorphs upon activating a Chaos Device
 	MORPH_FAILNOTELEFRAG	= 0x00000010,	// Player stays morphed if unmorph by Tome of Power fails
 	MORPH_FAILNOLAUGH		= 0x00000020,	// Player doesn't laugh if unmorph by Chaos Device fails
-	MORPH_WHENINVULNERABLE	= 0x00000040,	// Player can morph (or scripted unmorph) when invulnerable but ONLY if doing it to themselves
+	MORPH_WHENINVULNERABLE	= 0x00000040,	// Player can morph when invulnerable but ONLY if doing it to themselves
 	MORPH_LOSEACTUALWEAPON	= 0x00000080,	// Player loses specified morph weapon only (not "whichever they have when unmorphing")
 	MORPH_NEWTIDBEHAVIOUR	= 0x00000100,	// Actor TID is by default transferred from the old actor to the new actor
 	MORPH_UNDOBYDEATH		= 0x00000200,	// Actor unmorphs when killed and (unless MORPH_UNDOBYDEATHSAVES) stays dead
@@ -32,7 +32,7 @@ class AMorphedMonster;
 
 bool P_MorphPlayer (player_t *activator, player_t *player, const PClass *morphclass, int duration = 0, int style = 0,
 					const PClass *enter_flash = NULL, const PClass *exit_flash = NULL);
-bool P_UndoPlayerMorph (player_t *activator, player_t *player, bool force = false);
+bool P_UndoPlayerMorph (player_t *activator, player_t *player, int unmorphflag = 0, bool force = false);
 bool P_MorphMonster (AActor *actor, const PClass *morphclass, int duration = 0, int style = 0,
 					 const PClass *enter_flash = NULL, const PClass *exit_flash = NULL);
 bool P_UndoMonsterMorph (AMorphedMonster *beast, bool force = false);