diff --git a/Bartender4/MultiCastBar.lua b/Bartender4/MultiCastBar.lua
index fc138b2..db25865 100644
--- a/Bartender4/MultiCastBar.lua
+++ b/Bartender4/MultiCastBar.lua
@@ -7,11 +7,14 @@ if not HasMultiCastActionBar then return end
 
 local classMask = UnitClassMask("player")
 
--- CoA: the SHAMAN/HERO mask check doesn't know about CoA custom classes
--- (e.g. Witchdoctor, which also uses the totem bar). Fall back to the
--- game-created MultiCastActionBarFrame: if the engine produced it for this
--- player, we wrap it regardless of class.
-if not bit.contains(EnumUtil.CombineMasks(Enum.ClassMask.SHAMAN, Enum.ClassMask.HERO), classMask)
+-- CoA: Enum.ClassMask only knows vanilla classes (SHAMAN/HERO); custom classes
+-- (e.g. Witchdoctor) won't match. EnumUtil/Enum.ClassMask may also be nil on
+-- this client. Guard both: if the mask API is unavailable OR the player's class
+-- isn't in the vanilla set, fall through to the MultiCastActionBarFrame check —
+-- if the engine created the bar for this player we wrap it regardless of class.
+local _vanillaMask = EnumUtil and Enum and Enum.ClassMask
+  and EnumUtil.CombineMasks(Enum.ClassMask.SHAMAN, Enum.ClassMask.HERO)
+if _vanillaMask and not bit.contains(_vanillaMask, classMask)
    and not MultiCastActionBarFrame then
 	return
 end
diff --git a/Bartender4/Options/MultiCastBar.lua b/Bartender4/Options/MultiCastBar.lua
index 889a184..c968116 100644
--- a/Bartender4/Options/MultiCastBar.lua
+++ b/Bartender4/Options/MultiCastBar.lua
@@ -7,9 +7,12 @@ if not HasMultiCastActionBar then return end
 
 local classMask = UnitClassMask("player")
 
--- CoA: see MultiCastBar.lua — same gate, same fallback so the options
--- panel is registered for custom classes (e.g. Witchdoctor) too.
-if not bit.contains(EnumUtil.CombineMasks(Enum.ClassMask.SHAMAN, Enum.ClassMask.HERO), classMask)
+-- CoA: see MultiCastBar.lua — same gate, same fallback so the options panel is
+-- registered for custom classes (e.g. Witchdoctor) too. Guard EnumUtil /
+-- Enum.ClassMask for nil in case they are absent on this client.
+local _vanillaMask = EnumUtil and Enum and Enum.ClassMask
+  and EnumUtil.CombineMasks(Enum.ClassMask.SHAMAN, Enum.ClassMask.HERO)
+if _vanillaMask and not bit.contains(_vanillaMask, classMask)
    and not MultiCastActionBarFrame then
 	return
 end