diff --git a/components/openmw-mp/Packets/BasePacket.hpp b/components/openmw-mp/Packets/BasePacket.hpp
index d2d1c0d3f..a0410e027 100644
--- a/components/openmw-mp/Packets/BasePacket.hpp
+++ b/components/openmw-mp/Packets/BasePacket.hpp
@@ -35,7 +35,7 @@ namespace mwmp
 
         static size_t headerSize()
         {
-            return (sizeof(packetID) + RakNet::RakNetGUID::size()); // packetID + RakNetGUID (uint64_t)
+            return (size_t)(1 + RakNet::RakNetGUID::size()); // packetID + RakNetGUID (uint64_t)
         }
 
         unsigned char GetPacketID()