diff --git a/BizHawk.Emulation.Cores/Libretro/LibretroApi.cs b/BizHawk.Emulation.Cores/Libretro/LibretroApi.cs
index 28875d5d47..db2286cd84 100644
--- a/BizHawk.Emulation.Cores/Libretro/LibretroApi.cs
+++ b/BizHawk.Emulation.Cores/Libretro/LibretroApi.cs
@@ -151,8 +151,8 @@ namespace BizHawk.Emulation.Cores.Libretro
 			public retro_system_info retro_system_info;
 			public retro_system_av_info retro_system_av_info;
 
-			public uint retro_serialize_size_initial; //size_t :(
-			public uint retro_serialize_size; //size_t :(
+			public ulong retro_serialize_size_initial; //size_t :(
+			public ulong retro_serialize_size; //size_t :(
 
 			public uint retro_region;
 			public uint retro_api_version;
diff --git a/BizHawk.Emulation.Cores/Libretro/LibretroApi_CMD.cs b/BizHawk.Emulation.Cores/Libretro/LibretroApi_CMD.cs
index 9bb5b6540c..21ceffb8b6 100644
--- a/BizHawk.Emulation.Cores/Libretro/LibretroApi_CMD.cs
+++ b/BizHawk.Emulation.Cores/Libretro/LibretroApi_CMD.cs
@@ -62,7 +62,7 @@ namespace BizHawk.Emulation.Cores.Libretro
 		{
 			Message(eMessage.CMD_UpdateSerializeSize);
 			WaitForCMD();
-			return comm->env.retro_serialize_size;
+			return (uint)comm->env.retro_serialize_size;
 		}
 
 		public bool CMD_Serialize(byte[] data)
diff --git a/BizHawk.Emulation.Cores/Libretro/LibretroApi_Structs.cs b/BizHawk.Emulation.Cores/Libretro/LibretroApi_Structs.cs
index 24cfaea56c..0c50eeaa39 100644
--- a/BizHawk.Emulation.Cores/Libretro/LibretroApi_Structs.cs
+++ b/BizHawk.Emulation.Cores/Libretro/LibretroApi_Structs.cs
@@ -30,7 +30,7 @@ namespace BizHawk.Emulation.Cores.Libretro
 			public sbyte* valid_extensions;
 			public bool need_fullpath;
 			public bool block_extract;
-			public short pad;
+			short _pad;
 		}
 
 		public struct retro_system_timing
diff --git a/BizHawk.Emulation.Cores/Libretro/LibretroCore.cs b/BizHawk.Emulation.Cores/Libretro/LibretroCore.cs
index 623c1ef01e..243688c6f0 100644
--- a/BizHawk.Emulation.Cores/Libretro/LibretroCore.cs
+++ b/BizHawk.Emulation.Cores/Libretro/LibretroCore.cs
@@ -375,7 +375,7 @@ namespace BizHawk.Emulation.Cores.Libretro
 		public void SaveStateBinary(System.IO.BinaryWriter writer)
 		{
 			api.CMD_UpdateSerializeSize();
-			if (savebuff == null || savebuff.Length != api.comm->env.retro_serialize_size)
+			if (savebuff == null || savebuff.Length != (int)api.comm->env.retro_serialize_size)
 			{
 				savebuff = new byte[api.comm->env.retro_serialize_size];
 				savebuff2 = new byte[savebuff.Length + 13];
@@ -406,7 +406,7 @@ namespace BizHawk.Emulation.Cores.Libretro
 		public byte[] SaveStateBinary()
 		{
 			api.CMD_UpdateSerializeSize();
-			if (savebuff == null || savebuff.Length != api.comm->env.retro_serialize_size)
+			if (savebuff == null || savebuff.Length != (int)api.comm->env.retro_serialize_size)
 			{
 				savebuff = new byte[api.comm->env.retro_serialize_size];
 				savebuff2 = new byte[savebuff.Length + 13];