diff --git a/OpenRA.Game/FileSystem/MixFile.cs b/OpenRA.Game/FileSystem/MixFile.cs
index 7a36fb7e15..8a8f7b0d6e 100644
--- a/OpenRA.Game/FileSystem/MixFile.cs
+++ b/OpenRA.Game/FileSystem/MixFile.cs
@@ -191,9 +191,22 @@ namespace OpenRA.FileSystem
 		public Stream GetContent(PackageEntry entry)
 		{
 			Stream parentStream;
-			var offset = dataStart + entry.Offset + SegmentStream.GetOverallNestedOffset(s, out parentStream);
-			var path = ((FileStream)parentStream).Name;
-			return new SegmentStream(File.OpenRead(path), offset, entry.Length);
+			var baseOffset = dataStart + entry.Offset;
+			var nestedOffset = baseOffset + SegmentStream.GetOverallNestedOffset(s, out parentStream);
+
+			// Special case FileStream - instead of creating an in-memory copy,
+			// just reference the portion of the on-disk file that we need to save memory.
+			// We use GetType instead of 'is' here since we can't handle any derived classes of FileStream.
+			if (parentStream.GetType() == typeof(FileStream))
+			{
+				var path = ((FileStream)parentStream).Name;
+				return new SegmentStream(File.OpenRead(path), nestedOffset, entry.Length);
+			}
+
+			// For all other streams, create a copy in memory.
+			// This uses more memory but is the only way in general to ensure the returned streams won't clash.
+			s.Seek(baseOffset, SeekOrigin.Begin);
+			return new MemoryStream(s.ReadBytes((int)entry.Length));
 		}
 
 		public Stream GetStream(string filename)