diff --git a/karapace/protobuf/io.py b/karapace/protobuf/io.py
index cbead3913..dbf6f2211 100644
--- a/karapace/protobuf/io.py
+++ b/karapace/protobuf/io.py
@@ -3,7 +3,7 @@
 See LICENSE for details
 """
 from io import BytesIO
-from karapace.protobuf.encoding_variants import read_indexes, write_indexes
+from karapace.protobuf.varint import read_indexes, write_indexes
 from karapace.protobuf.exception import IllegalArgumentException, ProtobufSchemaResolutionException, ProtobufTypeException
 from karapace.protobuf.message_element import MessageElement
 from karapace.protobuf.protobuf_to_dict import dict_to_protobuf, protobuf_to_dict
diff --git a/karapace/protobuf/encoding_variants.py b/karapace/protobuf/varint.py
similarity index 75%
rename from karapace/protobuf/encoding_variants.py
rename to karapace/protobuf/varint.py
index 37e1d3cb9..cb9e2ee7f 100644
--- a/karapace/protobuf/encoding_variants.py
+++ b/karapace/protobuf/varint.py
@@ -5,11 +5,12 @@
 # Workaround to encode/decode indexes in protobuf messages
 # Based on https://developers.google.com/protocol-buffers/docs/encoding#varints
 
+from __future__ import annotations
 from io import BytesIO
 from karapace.protobuf.exception import IllegalArgumentException
-from typing import List
+from typing import List, Final, Sequence
 
-ZERO_BYTE = b"\x00"
+ZERO_BYTE: Final = b"\x00"
 
 
 def read_varint(bio: BytesIO) -> int:
@@ -35,25 +36,21 @@ def read_varint(bio: BytesIO) -> int:
 
 def read_indexes(bio: BytesIO) -> List[int]:
     try:
-        size: int = read_varint(bio)
+        size = read_varint(bio)
     except EOFError:
         # TODO: change exception
-        # pylint: disable=raise-missing-from
-        raise IllegalArgumentException("problem with reading binary data")
-    if size == 0:
-        return [0]
+        raise IllegalArgumentException("problem with reading binary data") from None
     return [read_varint(bio) for _ in range(size)]
 
 
-def write_varint(bio: BytesIO, value: int) -> int:
+def write_varint(bio: BytesIO, value: int) -> None:
     if value < 0:
         raise ValueError(f"value must not be negative, got {value}")
 
     if value == 0:
         bio.write(ZERO_BYTE)
-        return 1
+        return
 
-    written_bytes = 0
     while value > 0:
         to_write = value & 0x7F
         value = value >> 7
@@ -61,12 +58,10 @@ def write_varint(bio: BytesIO, value: int) -> int:
         if value > 0:
             to_write |= 0x80
 
-        bio.write(bytearray(to_write)[0])
-        written_bytes += 1
+        bio.write(to_write.to_bytes(1, "little"))
 
-    return written_bytes
 
-
-def write_indexes(bio: BytesIO, indexes: List[int]) -> None:
+def write_indexes(bio: BytesIO, indexes: Sequence[int]) -> None:
+    write_varint(bio, len(indexes))
     for i in indexes:
         write_varint(bio, i)
diff --git a/tests/unit/protobuf/test_varint.py b/tests/unit/protobuf/test_varint.py
new file mode 100644
index 000000000..49502bccc
--- /dev/null
+++ b/tests/unit/protobuf/test_varint.py
@@ -0,0 +1,35 @@
+from __future__ import annotations
+import io
+from hypothesis import given, example
+from hypothesis.strategies import integers, lists
+
+from karapace.protobuf.varint import write_varint, read_varint, read_indexes, \
+    write_indexes
+
+varint_values = integers(min_value=0)
+
+
+@given(varint_values)
+@example(0)
+@example(1)
+def test_can_roundtrip_varint(value: int) -> None:
+    with io.BytesIO() as buffer:
+        write_varint(buffer, value)
+        buffer.seek(0)
+        result = read_varint(buffer)
+        assert result == value
+        # Assert buffer is exhausted.
+        assert buffer.read(1) == b""
+
+
+@given(lists(elements=varint_values))
+@example([])
+@example([1, 2, 3])
+def test_can_roundtrip_indexes(value: list[int]) -> None:
+    with io.BytesIO() as buffer:
+        write_indexes(buffer, value)
+        buffer.seek(0)
+        result = read_indexes(buffer)
+        assert result == value
+        # Assert buffer is exhausted.
+        assert buffer.read(1) == b""