diff --git a/minecraft/__init__.py b/minecraft/__init__.py
index 722abed..d037b49 100644
--- a/minecraft/__init__.py
+++ b/minecraft/__init__.py
@@ -232,6 +232,7 @@ SUPPORTED_MINECRAFT_VERSIONS = {
     '20w10a':               705,
     '20w11a':               706,
     '20w12a':               707,
+    '20w13a':               708,
 }
 
 # Those Minecraft versions supported by pyCraft which are "release" versions,
diff --git a/minecraft/networking/types/basic.py b/minecraft/networking/types/basic.py
index 99aeba0..b2b1166 100644
--- a/minecraft/networking/types/basic.py
+++ b/minecraft/networking/types/basic.py
@@ -253,6 +253,14 @@ class VarIntPrefixedByteArray(Type):
         socket.send(struct.pack(str(len(value)) + "s", value))
 
 
+# https://stackoverflow.com/questions/1604464/twos-complement-in-python
+def twos_comp(val, bits):
+    """compute the 2's complement of int value val"""
+    if (val & (1 << (bits - 1))) != 0:  # if sign bit is set
+        val = val - (1 << bits)         # compute negative value
+    return val                          # return positive value as is
+
+
 class UUIDIntegerArray(Type):
     """ Minecraft sends an array of 4 integers to represent the most
         significant and least significant bits (as longs) of a UUID
@@ -263,7 +271,7 @@ class UUIDIntegerArray(Type):
     def read(file_object):
         ints = struct.unpack("4i", file_object.read(4 * 4))
         packed = struct.pack("<qq", ints[1] << 32 | ints[0] & 0xffffffff,
-            ints[3] << 32 | ints[2] & 0xffffffff)
+                             ints[3] << 32 | ints[2] & 0xffffffff)
         packed_uuid = uuid.UUID(bytes=packed)
         return str(packed_uuid)
 
@@ -271,8 +279,12 @@ class UUIDIntegerArray(Type):
     def send(value, socket):
         player_uuid = uuid.UUID(value)
         msb, lsb = struct.unpack(">qq", player_uuid.bytes)
-        socket.send(struct.pack("4i", msb & 0xffffffff, msb >> 32,
-            lsb & 0xffffffff, lsb >> 32))
+        socket.send(struct.pack(">4i", msb >> 32,
+                                twos_comp(msb & 0xffffffff, 32),
+                                lsb >> 32,
+                                twos_comp(lsb & 0xffffffff, 32)
+                                )
+                    )
 
 
 class TrailingByteArray(Type):