diff --git a/src/lua_baselib.c b/src/lua_baselib.c
index 1488f4024..525f2fe68 100644
--- a/src/lua_baselib.c
+++ b/src/lua_baselib.c
@@ -295,8 +295,8 @@ static int lib_pSpawnMobj(lua_State *L)
 	fixed_t z = luaL_checkfixed(L, 3);
 	mobjtype_t type = luaL_checkinteger(L, 4);
 	NOHUD
-	if (type > MT_LASTFREESLOT)
-		return luaL_error(L, "mobjtype_t out of bounds error!");
+	if (type >= NUMMOBJTYPES)
+		return luaL_error(L, "mobj type %d out of range (0 - %d)", type, NUMMOBJTYPES-1);
 	LUA_PushUserdata(L, P_SpawnMobj(x, y, z, type), META_MOBJ);
 	return 1;
 }
@@ -321,8 +321,8 @@ static int lib_pSpawnMissile(lua_State *L)
 	NOHUD
 	if (!source || !dest)
 		return LUA_ErrInvalid(L, "mobj_t");
-	if (type > MT_LASTFREESLOT)
-		return luaL_error(L, "mobjtype_t out of bounds error!");
+	if (type >= NUMMOBJTYPES)
+		return luaL_error(L, "mobj type %d out of range (0 - %d)", type, NUMMOBJTYPES-1);
 	LUA_PushUserdata(L, P_SpawnMissile(source, dest, type), META_MOBJ);
 	return 1;
 }
@@ -338,8 +338,8 @@ static int lib_pSpawnXYZMissile(lua_State *L)
 	NOHUD
 	if (!source || !dest)
 		return LUA_ErrInvalid(L, "mobj_t");
-	if (type > MT_LASTFREESLOT)
-		return luaL_error(L, "mobjtype_t out of bounds error!");
+	if (type >= NUMMOBJTYPES)
+		return luaL_error(L, "mobj type %d out of range (0 - %d)", type, NUMMOBJTYPES-1);
 	LUA_PushUserdata(L, P_SpawnXYZMissile(source, dest, type, x, y, z), META_MOBJ);
 	return 1;
 }
@@ -357,8 +357,8 @@ static int lib_pSpawnPointMissile(lua_State *L)
 	NOHUD
 	if (!source)
 		return LUA_ErrInvalid(L, "mobj_t");
-	if (type > MT_LASTFREESLOT)
-		return luaL_error(L, "mobjtype_t out of bounds error!");
+	if (type >= NUMMOBJTYPES)
+		return luaL_error(L, "mobj type %d out of range (0 - %d)", type, NUMMOBJTYPES-1);
 	LUA_PushUserdata(L, P_SpawnPointMissile(source, xa, ya, za, type, x, y, z), META_MOBJ);
 	return 1;
 }
@@ -374,8 +374,8 @@ static int lib_pSpawnAlteredDirectionMissile(lua_State *L)
 	NOHUD
 	if (!source)
 		return LUA_ErrInvalid(L, "mobj_t");
-	if (type > MT_LASTFREESLOT)
-		return luaL_error(L, "mobjtype_t out of bounds error!");
+	if (type >= NUMMOBJTYPES)
+		return luaL_error(L, "mobj type %d out of range (0 - %d)", type, NUMMOBJTYPES-1);
 	LUA_PushUserdata(L, P_SpawnAlteredDirectionMissile(source, type, x, y, z, shiftingAngle), META_MOBJ);
 	return 1;
 }
@@ -403,8 +403,8 @@ static int lib_pSPMAngle(lua_State *L)
 	NOHUD
 	if (!source)
 		return LUA_ErrInvalid(L, "mobj_t");
-	if (type > MT_LASTFREESLOT)
-		return luaL_error(L, "mobjtype_t out of bounds error!");
+	if (type >= NUMMOBJTYPES)
+		return luaL_error(L, "mobj type %d out of range (0 - %d)", type, NUMMOBJTYPES-1);
 	LUA_PushUserdata(L, P_SPMAngle(source, type, angle, allowaim, flags2), META_MOBJ);
 	return 1;
 }
@@ -417,8 +417,8 @@ static int lib_pSpawnPlayerMissile(lua_State *L)
 	NOHUD
 	if (!source)
 		return LUA_ErrInvalid(L, "mobj_t");
-	if (type > MT_LASTFREESLOT)
-		return luaL_error(L, "mobjtype_t out of bounds error!");
+	if (type >= NUMMOBJTYPES)
+		return luaL_error(L, "mobj type %d out of range (0 - %d)", type, NUMMOBJTYPES-1);
 	LUA_PushUserdata(L, P_SpawnPlayerMissile(source, type, flags2), META_MOBJ);
 	return 1;
 }
@@ -437,8 +437,8 @@ static int lib_pWeaponOrPanel(lua_State *L)
 {
 	mobjtype_t type = luaL_checkinteger(L, 1);
 	//HUDSAFE
-	if (type > MT_LASTFREESLOT)
-		return luaL_error(L, "mobjtype_t out of bounds error!");
+	if (type >= NUMMOBJTYPES)
+		return luaL_error(L, "mobj type %d out of range (0 - %d)", type, NUMMOBJTYPES-1);
 	lua_pushboolean(L, P_WeaponOrPanel(type));
 	return 1;
 }
@@ -477,8 +477,10 @@ static int lib_pSpawnParaloop(lua_State *L)
 	statenum_t nstate = luaL_optinteger(L, 8, S_NULL);
 	boolean spawncenter = lua_optboolean(L, 9);
 	NOHUD
-	if (type > MT_LASTFREESLOT)
-		return luaL_error(L, "mobjtype_t out of bounds error!");
+	if (type >= NUMMOBJTYPES)
+		return luaL_error(L, "mobj type %d out of range (0 - %d)", type, NUMMOBJTYPES-1);
+	if (nstate >= NUMSTATES)
+		return luaL_error(L, "state %d out of range (0 - %d)", nstate, NUMSTATES-1);
 	P_SpawnParaloop(x, y, z, radius, number, type, nstate, rotangle, spawncenter);
 	return 0;
 }
@@ -908,8 +910,8 @@ static int lib_pSpawnSpinMobj(lua_State *L)
 	NOHUD
 	if (!player)
 		return LUA_ErrInvalid(L, "player_t");
-	if (type > MT_LASTFREESLOT)
-		return luaL_error(L, "mobjtype_t out of bounds error!");
+	if (type >= NUMMOBJTYPES)
+		return luaL_error(L, "mobj type %d out of range (0 - %d)", type, NUMMOBJTYPES-1);
 	P_SpawnSpinMobj(player, type);
 	return 0;
 }
@@ -1274,6 +1276,8 @@ static int lib_pSetMobjStateNF(lua_State *L)
 	NOHUD
 	if (!mobj)
 		return LUA_ErrInvalid(L, "mobj_t");
+	if (state >= NUMSTATES)
+		return luaL_error(L, "state %d out of range (0 - %d)", state, NUMSTATES-1);
 	if (mobj->player && state == S_NULL)
 		return luaL_error(L, "Attempt to remove player mobj with S_NULL.");
 	lua_pushboolean(L, P_SetMobjStateNF(mobj, state));
@@ -1385,8 +1389,8 @@ static int lib_pIsFlagAtBase(lua_State *L)
 {
 	mobjtype_t flag = luaL_checkinteger(L, 1);
 	NOHUD
-	if (flag > MT_LASTFREESLOT)
-		return luaL_error(L, "mobjtype_t out of bounds error!");
+	if (flag >= NUMMOBJTYPES)
+		return luaL_error(L, "mobj type %d out of range (0 - %d)", flag, NUMMOBJTYPES-1);
 	lua_pushboolean(L, P_IsFlagAtBase(flag));
 	return 1;
 }
@@ -1619,7 +1623,7 @@ static int lib_rSetPlayerSkin(lua_State *L)
 	{
 		INT32 i = luaL_checkinteger(L, 2);
 		if (i < 0 || i >= MAXSKINS)
-			return luaL_error(L, "argument #2 cannot exceed MAXSKINS");
+			return luaL_error(L, "skin number (argument #2) %d out of range (0 - %d)", i, MAXSKINS-1);
 		SetPlayerSkinByNum(player-players, i);
 	}
 	else // skin name
@@ -1639,6 +1643,8 @@ static int lib_sStartSound(lua_State *L)
 	sfxenum_t sound_id = luaL_checkinteger(L, 2);
 	player_t *player = NULL;
 	NOHUD
+	if (sound_id >= NUMSFX)
+		return luaL_error(L, "sfx %d out of range (0 - %d)", sound_id, NUMSFX-1);
 	if (!lua_isnil(L, 1))
 	{
 		origin = *((mobj_t **)luaL_checkudata(L, 1, META_MOBJ));
@@ -1663,12 +1669,15 @@ static int lib_sStartSoundAtVolume(lua_State *L)
 	INT32 volume = (INT32)luaL_checkinteger(L, 3);
 	player_t *player = NULL;
 	NOHUD
+
 	if (!lua_isnil(L, 1))
 	{
 		origin = *((mobj_t **)luaL_checkudata(L, 1, META_MOBJ));
 		if (!origin)
 			return LUA_ErrInvalid(L, "mobj_t");
 	}
+	if (sound_id >= NUMSFX)
+		return luaL_error(L, "sfx %d out of range (0 - %d)", sound_id, NUMSFX-1);
 	if (!lua_isnone(L, 4) && lua_isuserdata(L, 4))
 	{
 		player = *((player_t **)luaL_checkudata(L, 4, META_PLAYER));
@@ -1800,6 +1809,8 @@ static int lib_sIdPlaying(lua_State *L)
 {
 	sfxenum_t id = luaL_checkinteger(L, 1);
 	NOHUD
+	if (id >= NUMSFX)
+		return luaL_error(L, "sfx %d out of range (0 - %d)", id, NUMSFX-1);
 	lua_pushboolean(L, S_IdPlaying(id));
 	return 1;
 }
@@ -1811,6 +1822,8 @@ static int lib_sSoundPlaying(lua_State *L)
 	NOHUD
 	if (!origin)
 		return LUA_ErrInvalid(L, "mobj_t");
+	if (id >= NUMSFX)
+		return luaL_error(L, "sfx %d out of range (0 - %d)", id, NUMSFX-1);
 	lua_pushboolean(L, S_SoundPlaying(origin, id));
 	return 1;
 }
@@ -1831,7 +1844,7 @@ static int lib_gDoReborn(lua_State *L)
 	INT32 playernum = luaL_checkinteger(L, 1);
 	NOHUD
 	if (playernum >= MAXPLAYERS)
-		return luaL_error(L, "playernum out of bounds error!");
+		return luaL_error(L, "playernum %d out of range (0 - %d)", playernum, MAXPLAYERS-1);
 	G_DoReborn(playernum);
 	return 0;
 }
diff --git a/src/lua_hudlib.c b/src/lua_hudlib.c
index 52770a88a..c4a72f074 100644
--- a/src/lua_hudlib.c
+++ b/src/lua_hudlib.c
@@ -166,6 +166,8 @@ static int lib_getHudInfo(lua_State *L)
 	lua_remove(L, 1);
 
 	i = luaL_checkinteger(L, 1);
+	if (i >= NUMHUDITEMS)
+		return luaL_error(L, "hudinfo[] index %d out of range (0 - %d)", i, NUMHUDITEMS-1);
 	LUA_PushUserdata(L, &hudinfo[i], META_HUDINFO);
 	return 1;
 }
diff --git a/src/lua_infolib.c b/src/lua_infolib.c
index 0fddebaba..6c99e4f6e 100644
--- a/src/lua_infolib.c
+++ b/src/lua_infolib.c
@@ -146,6 +146,8 @@ static int lib_getState(lua_State *L)
 	lua_remove(L, 1);
 
 	i = luaL_checkinteger(L, 1);
+	if (i >= NUMSTATES)
+		return luaL_error(L, "states[] index %d out of range (0 - %d)", i, NUMSTATES-1);
 	LUA_PushUserdata(L, &states[i], META_STATE);
 	return 1;
 }
@@ -155,7 +157,12 @@ static int lib_setState(lua_State *L)
 {
 	state_t *state;
 	lua_remove(L, 1); // don't care about states[] userdata.
-	state = &states[luaL_checkinteger(L, 1)]; // get the state to assign to.
+	{
+		UINT32 i = luaL_checkinteger(L, 1);
+		if (i >= NUMSTATES)
+			return luaL_error(L, "states[] index %d out of range (0 - %d)", i, NUMSTATES-1);
+		state = &states[i]; // get the state to assign to.
+	}
 	luaL_checktype(L, 2, LUA_TTABLE); // check that we've been passed a table.
 	lua_remove(L, 1); // pop state num, don't need it any more.
 	lua_settop(L, 1); // cut the stack here. the only thing left now is the table of data we're assigning to the state.
@@ -436,6 +443,8 @@ static int lib_getMobjInfo(lua_State *L)
 	lua_remove(L, 1);
 
 	i = luaL_checkinteger(L, 1);
+	if (i >= NUMMOBJTYPES)
+		return luaL_error(L, "mobjinfo[] index %d out of range (0 - %d)", i, NUMMOBJTYPES-1);
 	LUA_PushUserdata(L, &mobjinfo[i], META_MOBJINFO);
 	return 1;
 }
@@ -445,7 +454,12 @@ static int lib_setMobjInfo(lua_State *L)
 {
 	mobjinfo_t *info;
 	lua_remove(L, 1); // don't care about mobjinfo[] userdata.
-	info = &mobjinfo[luaL_checkinteger(L, 1)]; // get the mobjinfo to assign to.
+	{
+		UINT32 i = luaL_checkinteger(L, 1);
+		if (i >= NUMMOBJTYPES)
+			return luaL_error(L, "mobjinfo[] index %d out of range (0 - %d)", i, NUMMOBJTYPES-1);
+		info = &mobjinfo[i]; // get the mobjinfo to assign to.
+	}
 	luaL_checktype(L, 2, LUA_TTABLE); // check that we've been passed a table.
 	lua_remove(L, 1); // pop mobjtype num, don't need it any more.
 	lua_settop(L, 1); // cut the stack here. the only thing left now is the table of data we're assigning to the mobjinfo.
@@ -717,6 +731,8 @@ static int lib_getSfxInfo(lua_State *L)
 	lua_remove(L, 1);
 
 	i = luaL_checkinteger(L, 1);
+	if (i >= NUMSFX)
+		return luaL_error(L, "sfxinfo[] index %d out of range (0 - %d)", i, NUMSFX-1);
 	LUA_PushUserdata(L, &S_sfx[i], META_SFXINFO);
 	return 1;
 }
@@ -727,7 +743,12 @@ static int lib_setSfxInfo(lua_State *L)
 	sfxinfo_t *info;
 
 	lua_remove(L, 1);
-	info = &S_sfx[luaL_checkinteger(L, 1)]; // get the mobjinfo to assign to.
+	{
+		UINT32 i = luaL_checkinteger(L, 1);
+		if (i >= NUMSFX)
+			return luaL_error(L, "sfxinfo[] index %d out of range (0 - %d)", i, NUMSFX-1);
+		info = &S_sfx[i]; // get the mobjinfo to assign to.
+	}
 	luaL_checktype(L, 2, LUA_TTABLE); // check that we've been passed a table.
 	lua_remove(L, 1); // pop mobjtype num, don't need it any more.
 	lua_settop(L, 1); // cut the stack here. the only thing left now is the table of data we're assigning to the mobjinfo.
diff --git a/src/lua_playerlib.c b/src/lua_playerlib.c
index 53af2e3ac..388fe3175 100644
--- a/src/lua_playerlib.c
+++ b/src/lua_playerlib.c
@@ -55,7 +55,7 @@ static int lib_getPlayer(lua_State *L)
 	{
 		lua_Integer i = luaL_checkinteger(L, 2);
 		if (i < 0 || i >= MAXPLAYERS)
-			return luaL_error(L, "players[] index cannot exceed MAXPLAYERS");
+			return luaL_error(L, "players[] index %d out of range (0 - %d)", i, MAXPLAYERS-1);
 		if (!playeringame[i])
 			return 0;
 		if (!players[i].mo)
diff --git a/src/lua_skinlib.c b/src/lua_skinlib.c
index f07b4564c..545cf55b0 100644
--- a/src/lua_skinlib.c
+++ b/src/lua_skinlib.c
@@ -244,7 +244,7 @@ static int lib_getSkin(lua_State *L)
 	{
 		i = luaL_checkinteger(L, 2);
 		if (i < 0 || i >= MAXSKINS)
-			return luaL_error(L, "skins[] index cannot exceed MAXSKINS");
+			return luaL_error(L, "skins[] index %d out of range (0 - %d)", i, MAXSKINS-1);
 		if (i >= numskins)
 			return 0;
 		LUA_PushUserdata(L, &skins[i], META_SKIN);