diff --git a/BizHawk.Client.Common/IPS.cs b/BizHawk.Client.Common/IPS.cs
index 621ebe6a40..ccc9122b4f 100644
--- a/BizHawk.Client.Common/IPS.cs
+++ b/BizHawk.Client.Common/IPS.cs
@@ -5,7 +5,7 @@ namespace BizHawk.Client.Common
 {
 	public static class IPS
 	{
-		public static void Patch(byte[] rom, Stream patch)
+		public static byte[] Patch(byte[] rom, Stream patch)
 		{
 			var ipsHeader = new byte[5];
 			patch.Read(ipsHeader, 0, 5);
@@ -16,32 +16,40 @@ namespace BizHawk.Client.Common
 				if (ipsHeader[i] != header[i])
 				{
 					Console.WriteLine("Patch file specified is invalid.");
-					return;
+					return null;
 				}
 			}
 
 			// header verified, loop over patch entries
 			uint EOF = ('E' * 0x10000 + 'O' * 0x100 + 'F');
 
+			var ret = new MemoryStream(rom.Length);
+			ret.Write(rom, 0, rom.Length);
+
 			while (true)
 			{
 				uint offset = Read24(patch);
-				if (offset == EOF) return;
+				if (offset == EOF)
+					return ret.ToArray();
 				ushort size = Read16(patch);
 
+				ret.Seek(offset, SeekOrigin.Begin);
+
 				if (size != 0) // non-RLE patch
 				{
 					var patchData = new byte[size];
 					patch.Read(patchData, 0, size);
-					for (int i = 0; i < size; i++)
-						rom[offset++] = patchData[i];
+
+					ret.Write(patchData, 0, patchData.Length);
 				}
 				else // RLE patch
 				{
 					size = Read16(patch);
 					byte value = (byte)patch.ReadByte();
 					for (int i = 0; i < size; i++)
-						rom[offset++] = value;
+					{
+						ret.WriteByte(value);
+					}
 				}
 			}
 		}
diff --git a/BizHawk.Client.Common/RomGame.cs b/BizHawk.Client.Common/RomGame.cs
index 8c526cb2fd..8e4cbdcc1f 100644
--- a/BizHawk.Client.Common/RomGame.cs
+++ b/BizHawk.Client.Common/RomGame.cs
@@ -90,7 +90,7 @@ namespace BizHawk.Client.Common
 					patchFile.BindFirstOf("IPS");
 					if (patchFile.IsBound)
 					{
-						IPS.Patch(RomData, patchFile.GetStream());
+						RomData = IPS.Patch(RomData, patchFile.GetStream());
 					}
 				}
 			}