diff --git a/Source/missiles.cpp b/Source/missiles.cpp
index 87f05f99a..cad226952 100644
--- a/Source/missiles.cpp
+++ b/Source/missiles.cpp
@@ -3025,7 +3025,7 @@ void MI_Town(int i)
 		missile[i]._miVar2++;
 	}
 
-	for (p = 0; p < 4; p++) {
+	for (p = 0; p < MAX_PLRS; p++) {
 		if (plr[p].plractive && currlevel == plr[p].plrlevel && !plr[p]._pLvlChanging && !plr[p]._pmode && plr[p].WorldX == missile[i]._mix && plr[p].WorldY == missile[i]._miy) {
 			ClrPlrPath(p);
 			if (p == myplr) {
diff --git a/Source/monster.cpp b/Source/monster.cpp
index 68ddd7b35..7301a6b35 100644
--- a/Source/monster.cpp
+++ b/Source/monster.cpp
@@ -1636,7 +1636,7 @@ void MonstStartKill(int i, int pnum, BOOL sendmsg)
 
 	if (pnum >= 0)
 		monster[i].mWhoHit |= 1 << pnum;
-	if (pnum < 4 && i > 4)
+	if (pnum < MAX_PLRS && i > MAX_PLRS)
 		AddPlrMonstExper(monster[i].mLevel, monster[i].mExp, monster[i].mWhoHit);
 	monstkills[monster[i].MType->mtype]++;
 	monster[i]._mhitpoints = 0;
@@ -1691,14 +1691,14 @@ void M2MStartKill(int i, int mid)
 	NetSendCmdLocParam1(FALSE, CMD_MONSTDEATH, monster[mid]._mx, monster[mid]._my, mid);
 
 	monster[mid].mWhoHit |= 1 << i;
-	if (i < 4)
+	if (i < MAX_PLRS)
 		AddPlrMonstExper(monster[mid].mLevel, monster[mid].mExp, monster[mid].mWhoHit);
 
 	monstkills[monster[mid].MType->mtype]++;
 	monster[mid]._mhitpoints = 0;
 	SetRndSeed(monster[mid]._mRndSeed);
 
-	if (mid >= 4)
+	if (mid >= MAX_PLRS)
 		SpawnItem(mid, monster[mid]._mx, monster[mid]._my, TRUE);
 
 	if (monster[mid].MType->mtype == MT_DIABLO)
@@ -4484,7 +4484,7 @@ void DeleteMonsterList()
 	while (i < nummonsters) {
 		if (monster[monstactive[i]]._mDelFlag) {
 			DeleteMonster(i);
-			i = 0; // TODO: check if this should be i=4.
+			i = 0; // TODO: check if this should be MAX_PLRS.
 		} else {
 			i++;
 		}
@@ -5506,21 +5506,21 @@ int encode_enemy(int m)
 
 	enemy = monster[m]._menemy;
 	if (monster[m]._mFlags & MFLAG_TARGETS_MONSTER)
-		enemy += 4;
+		enemy += MAX_PLRS;
 
 	return enemy;
 }
 
 void decode_enemy(int m, int enemy)
 {
-	if (enemy < 4) {
+	if (enemy < MAX_PLRS) {
 		monster[m]._mFlags &= ~MFLAG_TARGETS_MONSTER;
 		monster[m]._menemy = enemy;
 		monster[m]._menemyx = plr[enemy]._px;
 		monster[m]._menemyy = plr[enemy]._py;
 	} else {
 		monster[m]._mFlags |= MFLAG_TARGETS_MONSTER;
-		enemy -= 4;
+		enemy -= MAX_PLRS;
 		monster[m]._menemy = enemy;
 		monster[m]._menemyx = monster[enemy]._mfutx;
 		monster[m]._menemyy = monster[enemy]._mfuty;
diff --git a/Source/msg.cpp b/Source/msg.cpp
index 0fd20006f..2641637ad 100644
--- a/Source/msg.cpp
+++ b/Source/msg.cpp
@@ -520,7 +520,7 @@ void DeltaLoadLevel()
 					decode_enemy(i, sgLevels[currlevel].monster[i]._menemy);
 					if (monster[i]._mx && monster[i]._mx != 1 || monster[i]._my)
 						dMonster[monster[i]._mx][monster[i]._my] = i + 1;
-					if (i < 4) {
+					if (i < MAX_PLRS) {
 						MAI_Golum(i);
 						monster[i]._mFlags |= (MFLAG_TARGETS_MONSTER | MFLAG_GOLEM);
 					} else {
diff --git a/Source/objects.cpp b/Source/objects.cpp
index 5db07998b..9cd8c0ba4 100644
--- a/Source/objects.cpp
+++ b/Source/objects.cpp
@@ -3480,13 +3480,13 @@ void OperateBookCase(int pnum, int i, BOOL sendmsg)
 			SetRndSeed(object[i]._oRndSeed);
 			CreateTypeItem(object[i]._ox, object[i]._oy, 0, ITYPE_MISC, IMISC_BOOK, sendmsg, 0);
 			if (QuestStatus(QTYPE_ZHAR)
-			    && monster[4].mName == UniqMonst[UMT_ZHAR].mName
-			    && monster[4]._msquelch == UCHAR_MAX
-			    && monster[4]._mhitpoints) {
-				monster[4].mtalkmsg = QUEST_ZHAR2;
-				M_StartStand(0, monster[4]._mdir);
-				monster[4]._mgoal = MGOAL_SHOOT;
-				monster[4]._mmode = MM_TALK;
+			    && monster[MAX_PLRS].mName == UniqMonst[UMT_ZHAR].mName
+			    && monster[MAX_PLRS]._msquelch == UCHAR_MAX
+			    && monster[MAX_PLRS]._mhitpoints) {
+				monster[MAX_PLRS].mtalkmsg = QUEST_ZHAR2;
+				M_StartStand(0, monster[MAX_PLRS]._mdir);
+				monster[MAX_PLRS]._mgoal = MGOAL_SHOOT;
+				monster[MAX_PLRS]._mmode = MM_TALK;
 			}
 			if (pnum == myplr)
 				NetSendCmdParam1(FALSE, CMD_OPERATEOBJ, i);