diff --git a/src/WattleScript.Interpreter/Tree/MemberUtilities.cs b/src/WattleScript.Interpreter/Tree/MemberUtilities.cs
index dd0efd87..0c550735 100644
--- a/src/WattleScript.Interpreter/Tree/MemberUtilities.cs
+++ b/src/WattleScript.Interpreter/Tree/MemberUtilities.cs
@@ -39,7 +39,7 @@ public static void AddModifierFlag(ref MemberModifierFlags source, Token token,
             
             foreach (var combo in flagConflicts)
             {
-                if (combo.appliesTo.HasFlag(memberType) && source.HasFlag(combo.a) && (combo.b == null || source.HasFlag(combo.b)))
+                if (combo.appliesTo.HasFlag(memberType) && source.HasFlag(combo.a) && (combo.b == null || source.HasFlag(combo.b.Value)))
                 {
                     if (combo.msg != null)
                         throw new SyntaxErrorException(token, combo.msg);