diff --git a/malduck/string/bin.py b/malduck/string/bin.py
index 289d416..3e37f8a 100644
--- a/malduck/string/bin.py
+++ b/malduck/string/bin.py
@@ -89,10 +89,9 @@ def pack(self, other: int, size: Optional[int] = None) -> bytes:
         :type size: bytes, optional
         :rtype: bytes
         """
-        packed = unhex(f"{other:x}")[::-1]
-        if size:
-            packed = packed[:size].ljust(size, b"\x00")
-        return packed
+        if size is None:
+            size = (other.bit_length() + 7) // 8
+        return other.to_bytes(size, byteorder="little")
 
     def unpack_be(self, other: bytes, size: Optional[int] = None) -> int:
         """
@@ -123,10 +122,9 @@ def pack_be(self, other: int, size: Optional[int] = None) -> bytes:
         :type size: bytes, optional
         :rtype: bytes
         """
-        packed = unhex(f"{other:x}")
-        if size:
-            packed = packed[:size].rjust(size, b"\x00")
-        return packed
+        if size is None:
+            size = (other.bit_length() + 7) // 8
+        return other.to_bytes(size, byteorder="big")
 
     def __call__(self, s, bitsize):
         warnings.warn(
diff --git a/tests/test_string.py b/tests/test_string.py
index 977876c..5ddfac9 100644
--- a/tests/test_string.py
+++ b/tests/test_string.py
@@ -120,6 +120,13 @@ def test_bigint():
     assert bigint.unpack_be(b"ABCDE", 4) == 0x41424344
     assert bigint.pack_be(0x41424344, 8) == b"\x00\x00\x00\x00ABCD"
 
+    assert bigint.pack(1) == b"\x01"
+    assert bigint.pack_be(1) == b"\x01"
+    assert bigint.pack(1234) == b"\xd2\x04"
+    assert bigint.pack_be(1234) == b"\x04\xd2"
+    assert bigint.unpack(b"\xd2\x04") == 1234
+    assert bigint.unpack_be(b"\x04\xd2") == 1234
+
 
 def test_pack():
     assert pack(