diff --git a/tests/unit/ast/nodes/test_fold_compare.py b/tests/unit/ast/nodes/test_fold_compare.py
index aab8ac0b2d..fd9f65a7d3 100644
--- a/tests/unit/ast/nodes/test_fold_compare.py
+++ b/tests/unit/ast/nodes/test_fold_compare.py
@@ -110,3 +110,20 @@ def test_compare_type_mismatch(op):
     old_node = vyper_ast.body[0].value
     with pytest.raises(UnfoldableNode):
         old_node.get_folded_value()
+
+
+@pytest.mark.parametrize("op", ["==", "!="])
+def test_compare_eq_bytes(get_contract, op):
+    left, right = "0xA1AAB33F", "0xa1aab33f"
+    source = f"""
+@external
+def foo(a: bytes4, b: bytes4) -> bool:
+    return a {op} b
+    """
+    contract = get_contract(source)
+
+    vyper_ast = parse_and_fold(f"{left} {op} {right}")
+    old_node = vyper_ast.body[0].value
+    new_node = old_node.get_folded_value()
+
+    assert contract.foo(left, right) == new_node.value
diff --git a/vyper/semantics/analysis/constant_folding.py b/vyper/semantics/analysis/constant_folding.py
index 6e4166dc52..98cab0f8cb 100644
--- a/vyper/semantics/analysis/constant_folding.py
+++ b/vyper/semantics/analysis/constant_folding.py
@@ -180,8 +180,11 @@ def visit_Compare(self, node):
             raise UnfoldableNode(
                 f"Invalid literal types for {node.op.description} comparison", node
             )
-
-        value = node.op._op(left.value, right.value)
+        lvalue, rvalue = left.value, right.value
+        if isinstance(left, vy_ast.Hex):
+            # Hex values are str, convert to be case-unsensitive.
+            lvalue, rvalue = lvalue.lower(), rvalue.lower()
+        value = node.op._op(lvalue, rvalue)
         return vy_ast.NameConstant.from_node(node, value=value)
 
     def visit_List(self, node) -> vy_ast.ExprNode:
diff --git a/vyper/utils.py b/vyper/utils.py
index f4f14a346e..3f19a9d15c 100644
--- a/vyper/utils.py
+++ b/vyper/utils.py
@@ -25,9 +25,10 @@ class OrderedSet(Generic[_T]):
     """
 
     def __init__(self, iterable=None):
-        self._data = dict()
-        if iterable is not None:
-            self.update(iterable)
+        if iterable is None:
+            self._data = dict()
+        else:
+            self._data = dict.fromkeys(iterable)
 
     def __repr__(self):
         keys = ", ".join(repr(k) for k in self)
@@ -57,6 +58,7 @@ def pop(self):
     def add(self, item: _T) -> None:
         self._data[item] = None
 
+    # NOTE to refactor: duplicate of self.update()
     def addmany(self, iterable):
         for item in iterable:
             self._data[item] = None
@@ -109,11 +111,11 @@ def intersection(cls, *sets):
         if len(sets) == 0:
             raise ValueError("undefined: intersection of no sets")
 
-        ret = sets[0].copy()
-        for e in sets[0]:
-            if any(e not in s for s in sets[1:]):
-                ret.remove(e)
-        return ret
+        tmp = sets[0]._data.keys()
+        for s in sets[1:]:
+            tmp &= s._data.keys()
+
+        return cls(tmp)
 
 
 class StringEnum(enum.Enum):