diff --git a/pgvector/bit.py b/pgvector/bit.py
index 098ebb2..a9370e4 100644
--- a/pgvector/bit.py
+++ b/pgvector/bit.py
@@ -88,7 +88,7 @@ def from_binary(cls, value: bytes | bytearray | memoryview, /) -> Bit:
         length, = unpack_from('>i', value)
         data = memoryview(value)[4:].tobytes()
 
-        if len(data) != (length + 7) // 8:
+        if length < 0 or len(data) != (length + 7) // 8:
             raise ValueError('invalid length')
 
         bit = cls.__new__(cls)
diff --git a/tests/test_bit.py b/tests/test_bit.py
index 6487348..ad1bd36 100644
--- a/tests/test_bit.py
+++ b/tests/test_bit.py
@@ -6,6 +6,16 @@
 
 
 class TestBit:
+    @pytest.mark.parametrize('length', [-1, -2, -7, -8])
+    def test_from_binary_negative_length(self, length: int) -> None:
+        with pytest.raises(ValueError, match='invalid length'):
+            Bit.from_binary(pack('>i', length))
+
+    @pytest.mark.parametrize('length', [0, 1, 7, 8, 9])
+    def test_from_binary_length_boundaries(self, length: int) -> None:
+        bit = Bit('1' * length)
+        assert Bit.from_binary(bit.to_binary()) == bit
+
     def test_list(self) -> None:
         assert Bit([True, False, True]).to_list() == [True, False, True]