diff --git a/Source/lighting.cpp b/Source/lighting.cpp
index 347b418ae..00b614b26 100644
--- a/Source/lighting.cpp
+++ b/Source/lighting.cpp
@@ -594,7 +594,7 @@ void SavePreLighting()
 	memcpy(dPreLight, dLight, sizeof(dPreLight));
 }
 
-void ActivateVision(Point position, int r, int id)
+void ActivateVision(Point position, int r, size_t id)
 {
 	auto &vision = VisionList[id];
 	vision.position.tile = position;
@@ -606,7 +606,7 @@ void ActivateVision(Point position, int r, int id)
 	UpdateVision = true;
 }
 
-void ChangeVisionRadius(int id, int r)
+void ChangeVisionRadius(size_t id, int r)
 {
 	auto &vision = VisionList[id];
 	vision.hasChanged = true;
@@ -616,7 +616,7 @@ void ChangeVisionRadius(int id, int r)
 	UpdateVision = true;
 }
 
-void ChangeVisionXY(int id, Point position)
+void ChangeVisionXY(size_t id, Point position)
 {
 	auto &vision = VisionList[id];
 	vision.hasChanged = true;
diff --git a/Source/lighting.h b/Source/lighting.h
index cb8c65607..f4404a067 100644
--- a/Source/lighting.h
+++ b/Source/lighting.h
@@ -74,9 +74,9 @@ void ChangeLightOffset(int i, DisplacementOf<int8_t> offset);
 void ChangeLight(int i, Point position, uint8_t radius);
 void ProcessLightList();
 void SavePreLighting();
-void ActivateVision(Point position, int r, int id);
-void ChangeVisionRadius(int id, int r);
-void ChangeVisionXY(int id, Point position);
+void ActivateVision(Point position, int r, size_t id);
+void ChangeVisionRadius(size_t id, int r);
+void ChangeVisionXY(size_t id, Point position);
 void ProcessVisionList();
 void lighting_color_cycling();
 
diff --git a/Source/multi.cpp b/Source/multi.cpp
index 9f117aae2..c9a3ec36b 100644
--- a/Source/multi.cpp
+++ b/Source/multi.cpp
@@ -192,7 +192,7 @@ void CheckPlayerInfoTimeouts()
 	}
 }
 
-void SendPacket(int playerId, const std::byte *packet, size_t size)
+void SendPacket(size_t playerId, const std::byte *packet, size_t size)
 {
 	TPkt pkt;
 
@@ -200,7 +200,7 @@ void SendPacket(int playerId, const std::byte *packet, size_t size)
 	const size_t sizeWithheader = size + sizeof(pkt.hdr);
 	pkt.hdr.wLen = SDL_SwapLE16(static_cast<uint16_t>(sizeWithheader));
 	memcpy(pkt.body, packet, size);
-	if (!SNetSendMessage(playerId, &pkt.hdr, sizeWithheader))
+	if (!SNetSendMessage(static_cast<int>(playerId), &pkt.hdr, sizeWithheader))
 		nthread_terminate_game("SNetSendMessage0");
 }
 
@@ -495,7 +495,7 @@ void InitGameInfo()
 	sgGameInitInfo.fullQuests = (!gbIsMultiplayer || *sgOptions.Gameplay.multiplayerFullQuests) ? 1 : 0;
 }
 
-void NetSendLoPri(int playerId, const std::byte *data, size_t size)
+void NetSendLoPri(size_t playerId, const std::byte *data, size_t size)
 {
 	if (data != nullptr && size != 0) {
 		CopyPacket(&lowPriorityBuffer, data, size);
@@ -503,7 +503,7 @@ void NetSendLoPri(int playerId, const std::byte *data, size_t size)
 	}
 }
 
-void NetSendHiPri(int playerId, const std::byte *data, size_t size)
+void NetSendHiPri(size_t playerId, const std::byte *data, size_t size)
 {
 	if (data != nullptr && size != 0) {
 		CopyPacket(&highPriorityBuffer, data, size);
diff --git a/Source/multi.h b/Source/multi.h
index bc8c5c804..efcaabb58 100644
--- a/Source/multi.h
+++ b/Source/multi.h
@@ -56,8 +56,8 @@ extern uint32_t player_state[MAX_PLRS];
 extern bool IsLoopback;
 
 void InitGameInfo();
-void NetSendLoPri(int playerId, const std::byte *data, size_t size);
-void NetSendHiPri(int playerId, const std::byte *data, size_t size);
+void NetSendLoPri(size_t playerId, const std::byte *data, size_t size);
+void NetSendHiPri(size_t playerId, const std::byte *data, size_t size);
 void multi_send_msg_packet(uint32_t pmask, const std::byte *data, size_t size);
 void multi_msg_countdown();
 void multi_player_left(int pnum, int reason);