diff --git a/source/md.c b/source/md.c
index dac5c46..78a2d6e 100644
--- a/source/md.c
+++ b/source/md.c
@@ -3377,11 +3377,18 @@ MD_ExprBakeOperatorTableFromList(MD_Arena *arena, MD_ExprOprList *list)
         {
             error_str = MD_S8Fmt(arena, "Invalid operator kind.");
         }
+        else if(op_kind != MD_ExprOprKind_Postfix &&
+                (MD_S8Match(op_s, MD_S8Lit("[]"), 0) || MD_S8Match(op_s, MD_S8Lit("()"), 0))){
+            error_str =
+                MD_S8Fmt(arena, "Ignored operator \"%.*s\". \"%.*s\" is only allowed as unary postfix",
+                         MD_S8VArg(op_s), MD_S8VArg(op_s));
+        }
+        else if(MD_S8Match(op_s, MD_S8Lit("[)"), 0) || MD_S8Match(op_s, MD_S8Lit("(]"), 0) ||
+                MD_S8Match(op_s, MD_S8Lit("{}"), 0)){
+            error_str = MD_S8Fmt(arena, "Ignored forbidden operator \"%.*s\".", MD_S8VArg(op_s));
+        }
         else
         {
-            // TODO(mal): Allow "[]" and "()" only as unary postfix
-            // TODO(mal): Disallow all other set types ("[)", "(]", "{}") from becoming operators
-
             for(MD_ExprOpr *op2 = list->first;
                 op2 != op;
                 op2 = op2->next)
diff --git a/tests/expression_tests.c b/tests/expression_tests.c
index e7cdc3b..976942c 100644
--- a/tests/expression_tests.c
+++ b/tests/expression_tests.c
@@ -239,7 +239,7 @@ operator_array[Op_##name].op = (MD_ExprOpr){ .op_id = Op_##name, .kind = MD_Expr
 #undef X 
     
     arena = MD_ArenaAlloc();
-    
+
     /* NOTE: Operator table bake errors */ 
     {
         MD_ExprOprList operator_list = {0};
@@ -247,7 +247,9 @@ operator_array[Op_##name].op = (MD_ExprOpr){ .op_id = Op_##name, .kind = MD_Expr
         
         MD_String8 plus = MD_S8Lit("+");
         MD_String8 minus = MD_S8Lit("-");
+        MD_String8 cast = MD_S8Lit("()");
         MD_Node *plus_node = MD_MakeNode(arena, MD_NodeKind_Main, plus, plus, 0);
+        MD_Node *cast_node = MD_MakeNode(arena, MD_NodeKind_Main, cast, cast, 0);
         MD_Node *minus_node = MD_MakeNode(arena, MD_NodeKind_Main, minus, minus, 0);
         MD_Node *plus_node_bis = MD_MakeNode(arena, MD_NodeKind_Main, plus, plus, 0);
         
@@ -259,6 +261,15 @@ operator_array[Op_##name].op = (MD_ExprOpr){ .op_id = Op_##name, .kind = MD_Expr
         MD_Assert(op_table.errors.max_message_kind == MD_MessageKind_Warning &&
                   op_table.errors.node_count == 1 && 
                   op_table.errors.first->user_ptr == plus_node);
+
+        // NOTE: () not as unary postfix
+        operator_list = (MD_ExprOprList){0};
+        MD_ExprOprPush(arena, &operator_list, MD_ExprOprKind_Prefix, 1, MD_S8Lit("()"),
+                       23 /* arbitrary MD_ExprOprKind */, cast_node);
+        op_table = MD_ExprBakeOperatorTableFromList(arena, &operator_list);
+        MD_Assert(op_table.errors.max_message_kind == MD_MessageKind_Warning &&
+                  op_table.errors.node_count == 1 && 
+                  op_table.errors.first->user_ptr == cast_node);
         
         // NOTE: Repeat operator
         operator_list = (MD_ExprOprList){0};