diff --git a/src/d_main.cpp b/src/d_main.cpp
index 7462f4250..4f0916a72 100644
--- a/src/d_main.cpp
+++ b/src/d_main.cpp
@@ -555,6 +555,7 @@ CVAR (Flag, sv_cooplosearmor,	dmflags, DF_COOP_LOSE_ARMOR);
 CVAR (Flag, sv_cooplosepowerups,	dmflags, DF_COOP_LOSE_POWERUPS);
 CVAR (Flag, sv_cooploseammo,	dmflags, DF_COOP_LOSE_AMMO);
 CVAR (Flag, sv_coophalveammo,	dmflags, DF_COOP_HALVE_AMMO);
+CVAR (Flag, sv_instantreaction,	dmflags, DF_INSTANT_REACTION);
 
 // Some (hopefully cleaner) interface to these settings.
 CVAR (Mask, sv_crouch,			dmflags, DF_NO_CROUCH|DF_YES_CROUCH);
diff --git a/src/doomdef.h b/src/doomdef.h
index df4d55999..1adf81d7d 100644
--- a/src/doomdef.h
+++ b/src/doomdef.h
@@ -136,6 +136,7 @@ enum
 	DF_COOP_LOSE_POWERUPS	= 1 << 28,	// Lose powerups when respawning in coop
 	DF_COOP_LOSE_AMMO		= 1 << 29,	// Lose ammo when respawning in coop
 	DF_COOP_HALVE_AMMO		= 1 << 30,	// Lose half your ammo when respawning in coop (but not less than the normal starting amount)
+	DF_INSTANT_REACTION		= 1 << 31,	// Monsters react instantly
 };
 
 // [BC] More dmflags. w00p!
diff --git a/src/playsim/p_mobj.cpp b/src/playsim/p_mobj.cpp
index 68583f8c8..fade8e640 100644
--- a/src/playsim/p_mobj.cpp
+++ b/src/playsim/p_mobj.cpp
@@ -4477,7 +4477,8 @@ void ConstructActor(AActor *actor, const DVector3 &pos, bool SpawningMapThing)
 
 	FRandom &rng = Level->BotInfo.m_Thinking ? pr_botspawnmobj : pr_spawnmobj;
 
-	if (!!G_SkillProperty(SKILLP_InstantReaction) && actor->flags3 & MF3_ISMONSTER)
+	if (!!(G_SkillProperty(SKILLP_InstantReaction) || !!(dmflags & DF_INSTANT_REACTION))
+		&& actor->flags3 & MF3_ISMONSTER)
 		actor->reactiontime = 0;
 
 	if (actor->flags3 & MF3_ISMONSTER)
diff --git a/src/sound/s_advsound.cpp b/src/sound/s_advsound.cpp
index cdc84b0a7..c0729bba6 100644
--- a/src/sound/s_advsound.cpp
+++ b/src/sound/s_advsound.cpp
@@ -1174,9 +1174,11 @@ static void S_AddSNDINFO (int lump)
 				if (lump >= 0)
 				{
 					// do not set the alias if a later WAD defines its own music of this name
+					// internal files (up to and including iwads) can always be set for musicalias
 					int file = fileSystem.GetFileContainer(lump);
 					int sndifile = fileSystem.GetFileContainer(sc.LumpNum);
-					if (!(sndifile == 1 && file <= fileSystem.GetIwadNum()) && (file > sndifile))
+					if ( (file > sndifile) &&
+						!(sndifile <= fileSystem.GetIwadNum() && file <= fileSystem.GetIwadNum()) )
 					{
 						sc.MustGetString();
 						continue;
diff --git a/wadsrc/static/menudef.txt b/wadsrc/static/menudef.txt
index 8341eba31..b2c5e58e5 100644
--- a/wadsrc/static/menudef.txt
+++ b/wadsrc/static/menudef.txt
@@ -1641,6 +1641,7 @@ OptionMenu GameplayOptions protected
 	Option "$GMPLYMNU_ITEMSRESPAWN",			"sv_itemrespawn", "YesNo"
 	Option "$GMPLYMNU_SUPERRESPAWN",			"sv_respawnsuper", "YesNo"
 	Option "$GMPLYMNU_FASTMONSTERS",			"sv_fastmonsters", "YesNo"
+	Option "$GMPLYMNU_INSTANTREACTION",			"sv_instantreaction", "YesNo"
 	Option "$GMPLYMNU_DEGENERATION",			"sv_degeneration", "YesNo"
 	Option "$GMPLYMNU_NOAUTOAIM",				"sv_noautoaim", "NoYes"
 	Option "$GMPLYMNU_ALLOWSUICIDE",			"sv_disallowsuicide", "NoYes"