diff --git a/OpenRA.Game/FileFormats/Blast.cs b/OpenRA.Game/FileFormats/Blast.cs
index 74d124b5a6..2f4ec39e52 100644
--- a/OpenRA.Game/FileFormats/Blast.cs
+++ b/OpenRA.Game/FileFormats/Blast.cs
@@ -57,10 +57,13 @@ namespace OpenRA.FileFormats
 		static Huffman lencode = new Huffman(lenlen, lenlen.Length, 16);
 		static Huffman distcode = new Huffman(distlen, distlen.Length, 64);
 
-		// Decode PKWare Compression Library stream.
-		public static byte[] Decompress(byte[] src)
+		/// <summary>PKWare Compression Library stream.</summary>
+		/// <param name="input">Compressed input stream.</param>
+		/// <param name="output">Stream to write the decompressed output.</param>
+		/// <param name="onProgress">Progress callback, invoked with (read bytes, written bytes).</param>
+		public static void Decompress(Stream input, Stream output, Action<long, long> onProgress = null)
 		{
-			var br = new BitReader(src);
+			var br = new BitReader(input);
 
 			// Are literals coded?
 			var coded = br.ReadBits(8);
@@ -78,7 +81,9 @@ namespace OpenRA.FileFormats
 			ushort next = 0; // index of next write location in out[]
 			var first = true; // true to check distances (for first 4K)
 			var outBuffer = new byte[MAXWIN]; // output buffer and sliding window
-			var ms = new MemoryStream();
+
+			var inputStart = input.Position;
+			var outputStart = output.Position;
 
 			// decode literals and length/distance pairs
 			do
@@ -94,7 +99,10 @@ namespace OpenRA.FileFormats
 					if (len == 519)
 					{
 						for (var i = 0; i < next; i++)
-							ms.WriteByte(outBuffer[i]);
+							output.WriteByte(outBuffer[i]);
+
+						if (onProgress != null)
+							onProgress(input.Position - inputStart, output.Position - outputStart);
 						break;
 					}
 
@@ -137,9 +145,12 @@ namespace OpenRA.FileFormats
 						if (next == MAXWIN)
 						{
 							for (var i = 0; i < next; i++)
-								ms.WriteByte(outBuffer[i]);
+								output.WriteByte(outBuffer[i]);
 							next = 0;
 							first = false;
+
+							if (onProgress != null)
+								onProgress(input.Position - inputStart, output.Position - outputStart);
 						}
 					} while (len != 0);
 				}
@@ -151,14 +162,15 @@ namespace OpenRA.FileFormats
 					if (next == MAXWIN)
 					{
 						for (var i = 0; i < next; i++)
-							ms.WriteByte(outBuffer[i]);
+							output.WriteByte(outBuffer[i]);
 						next = 0;
 						first = false;
+
+						if (onProgress != null)
+							onProgress(input.Position - inputStart, output.Position - outputStart);
 					}
 				}
 			} while (true);
-
-			return ms.ToArray();
 		}
 
 		// Decode a code using Huffman table h.
@@ -185,14 +197,13 @@ namespace OpenRA.FileFormats
 
 	class BitReader
 	{
-		readonly byte[] src;
-		int offset = 0;
-		int bitBuffer = 0;
+		readonly Stream stream;
+		byte bitBuffer = 0;
 		int bitCount = 0;
 
-		public BitReader(byte[] src)
+		public BitReader(Stream stream)
 		{
-			this.src = src;
+			this.stream = stream;
 		}
 
 		public int ReadBits(int count)
@@ -203,7 +214,7 @@ namespace OpenRA.FileFormats
 			{
 				if (bitCount == 0)
 				{
-					bitBuffer = src[offset++];
+					bitBuffer = stream.ReadUInt8();
 					bitCount = 8;
 				}
 
diff --git a/OpenRA.Game/FileSystem/InstallShieldPackage.cs b/OpenRA.Game/FileSystem/InstallShieldPackage.cs
index 5089edd74b..906299a54e 100644
--- a/OpenRA.Game/FileSystem/InstallShieldPackage.cs
+++ b/OpenRA.Game/FileSystem/InstallShieldPackage.cs
@@ -114,9 +114,12 @@ namespace OpenRA.FileSystem
 				return null;
 
 			s.Seek(dataStart + e.Offset, SeekOrigin.Begin);
-			var data = s.ReadBytes((int)e.Length);
 
-			return new MemoryStream(Blast.Decompress(data));
+			var ret = new MemoryStream();
+			Blast.Decompress(s, ret);
+			ret.Seek(0, SeekOrigin.Begin);
+
+			return ret;
 		}
 
 		public bool Contains(string filename)
diff --git a/OpenRA.Mods.Common/Widgets/Logic/Installation/InstallFromDiscLogic.cs b/OpenRA.Mods.Common/Widgets/Logic/Installation/InstallFromDiscLogic.cs
index b451812e6e..dbd28ceacb 100644
--- a/OpenRA.Mods.Common/Widgets/Logic/Installation/InstallFromDiscLogic.cs
+++ b/OpenRA.Mods.Common/Widgets/Logic/Installation/InstallFromDiscLogic.cs
@@ -183,13 +183,13 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 
 							case "extract-raw":
 							{
-								ExtractFromPackage(ExtractionType.Raw, path, i.Value, extracted, ref message);
+								ExtractFromPackage(ExtractionType.Raw, path, i.Value, extracted, m => message = m);
 								break;
 							}
 
 							case "extract-blast":
 							{
-								ExtractFromPackage(ExtractionType.Blast, path, i.Value, extracted, ref message);
+								ExtractFromPackage(ExtractionType.Blast, path, i.Value, extracted, m => message = m);
 								break;
 							}
 
@@ -228,7 +228,7 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 
 		enum ExtractionType { Raw, Blast }
 
-		static void ExtractFromPackage(ExtractionType type, string path, MiniYaml actionYaml, List<string> extractedFiles, ref string progressMessage)
+		static void ExtractFromPackage(ExtractionType type, string path, MiniYaml actionYaml, List<string> extractedFiles, Action<string> updateMessage)
 		{
 			var sourcePath = Path.Combine(path, actionYaml.Value);
 			using (var source = File.OpenRead(sourcePath))
@@ -265,15 +265,20 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 					Directory.CreateDirectory(Path.GetDirectoryName(targetPath));
 					using (var target = File.OpenWrite(targetPath))
 					{
-						// This is a bit dumb memory-wise, but we load the whole thing when running the game anyway
 						Log.Write("install", "Extracting {0} -> {1}".F(sourcePath, targetPath));
-						progressMessage = "Extracting " + Path.GetFileName(Path.GetFileName(targetPath));
-
-						var data = source.ReadBytes(length);
+						var displayFilename = Path.GetFileName(Path.GetFileName(targetPath));
 						if (type == ExtractionType.Blast)
-							data = Blast.Decompress(data);
-
-						target.Write(data);
+						{
+							Action<long, long> onProgress = (read, _) =>
+								updateMessage("Extracting " + displayFilename + " ({0}%)".F(100 * read / length));
+							Blast.Decompress(source, target, onProgress);
+						}
+						else
+						{
+							updateMessage("Extracting " + displayFilename);
+							// This is a bit dumb memory-wise, but we load the whole thing when running the game anyway
+							target.Write(source.ReadBytes(length));
+						}
 					}
 				}
 			}