diff --git a/Source/objects.cpp b/Source/objects.cpp
index b489fa3d7..2d51d4fab 100644
--- a/Source/objects.cpp
+++ b/Source/objects.cpp
@@ -2247,6 +2247,11 @@ void OperatePedestal(Player &player, Object &pedestal, bool sendmsg)
 	}
 }
 
+int ClampU8(int v)
+{
+	return std::clamp(v, 0, 255);
+}
+
 void OperateShrineMysterious(DiabloGenerator &rng, Player &player)
 {
 	if (&player != MyPlayer)
@@ -2331,24 +2336,24 @@ void OperateShrineGloomy(Player &player)
 	if (&player != MyPlayer)
 		return;
 
-	// Increment armor class by 2 and decrements max damage by 1.
 	for (Item &item : PlayerItemsRange(player)) {
 		switch (item._itype) {
 		case ItemType::Sword:
 		case ItemType::Axe:
 		case ItemType::Bow:
 		case ItemType::Mace:
-		case ItemType::Staff:
-			item._iMaxDam--;
-			if (item._iMaxDam < item._iMinDam)
-				item._iMaxDam = item._iMinDam;
-			break;
+		case ItemType::Staff: {
+			const int minDam = static_cast<int>(item._iMinDam);
+			const int maxDam = static_cast<int>(item._iMaxDam);
+			const int newMax = std::max(maxDam - 1, minDam);
+			item._iMaxDam = static_cast<uint8_t>(ClampU8(newMax));
+		} break;
 		case ItemType::Shield:
 		case ItemType::Helm:
 		case ItemType::LightArmor:
 		case ItemType::MediumArmor:
 		case ItemType::HeavyArmor:
-			item._iAC += 2;
+			item._iAC = ClampU8(item._iAC + 2);
 			break;
 		default:
 			break;
@@ -2356,7 +2361,6 @@ void OperateShrineGloomy(Player &player)
 	}
 
 	CalcPlrInv(player, true);
-
 	InitDiabloMsg(EMSG_SHRINE_GLOOMY);
 }