diff --git a/src/celpy/celtypes.py b/src/celpy/celtypes.py
index 8f6bf8f..71115e3 100644
--- a/src/celpy/celtypes.py
+++ b/src/celpy/celtypes.py
@@ -442,6 +442,9 @@ def __new__(
     def __repr__(self) -> str:
         return f"{self.__class__.__name__}({super().__repr__()})"
 
+    def contains(self, item: Value) -> BoolType:
+        return BoolType(cast(BytesType, item) in self)
+
 
 class DoubleType(float):
     """
diff --git a/tests/test_celtypes.py b/tests/test_celtypes.py
index f8cdd68..c0067f1 100644
--- a/tests/test_celtypes.py
+++ b/tests/test_celtypes.py
@@ -81,6 +81,7 @@ def test_bytes_type():
     assert repr(b_0) == "BytesType(b'bytes')"
     assert BytesType(None) == BytesType(b'')
     assert BytesType(MessageType({"value": BytesType(b'42')})) == BytesType(b'42')
+    assert b_0.contains(b'byte')
 
 
 def test_double_type():