diff --git a/LibOrbisPkg/PFS/PFSCReader.cs b/LibOrbisPkg/PFS/PFSCReader.cs
index 12c6c1b..3af97d3 100644
--- a/LibOrbisPkg/PFS/PFSCReader.cs
+++ b/LibOrbisPkg/PFS/PFSCReader.cs
@@ -84,7 +84,13 @@ public void ReadSector(int idx, byte[] output)
         using (var bufStream = new MemoryStream(sectorBuf))
         using (var ds = new DeflateStream(bufStream, CompressionMode.Decompress))
         {
-          ds.Read(output, 0, hdr.BlockSz);
+          // DeflateStream.Read may return fewer bytes than requested (.NET 6+ returns as soon as
+          // some output is available), so keep reading until the sector is full.
+          int got = 0, n;
+          while (got < hdr.BlockSz && (n = ds.Read(output, got, hdr.BlockSz - got)) > 0)
+            got += n;
+          if (got < hdr.BlockSz)
+            Array.Clear(output, got, hdr.BlockSz - got);
         }
       }
     }
diff --git a/LibOrbisPkgTests/PfscReaderTests.cs b/LibOrbisPkgTests/PfscReaderTests.cs
new file mode 100644
index 0000000..9bd9e84
--- /dev/null
+++ b/LibOrbisPkgTests/PfscReaderTests.cs
@@ -0,0 +1,75 @@
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using System;
+using System.Collections.Generic;
+using System.Globalization;
+using System.IO;
+using System.IO.Compression;
+using System.Linq;
+using System.Reflection;
+using System.Threading;
+using LibOrbisPkg.GP4;
+using LibOrbisPkg.PFS;
+using LibOrbisPkg.PKG;
+using LibOrbisPkg.Util;
+
+namespace LibOrbisPkgTests
+{
+  [TestClass]
+  public class PfscReaderTests
+  {
+    const int Block = 0x10000;
+
+    static byte[] MakePfsc(byte[] data, Func<int, bool> compressBlock)
+    {
+      int n = (data.Length + Block - 1) / Block;
+      long table = 8 + n * 8L;
+      long extra = ((table - 0xFC00) + 0xFFFF) / 0x10000;
+      long hdrSize = 0x10000 + (extra > 0 ? Block * extra : 0);
+      var blocks = new List<byte[]>();
+      for (int i = 0; i < n; i++)
+      {
+        var raw = new byte[Block];
+        Buffer.BlockCopy(data, i * Block, raw, 0, Math.Min(Block, data.Length - i * Block));
+        if (compressBlock(i))
+        {
+          using (var ms = new MemoryStream())
+          {
+            using (var z = new ZLibStream(ms, CompressionLevel.Optimal, true))
+              z.Write(raw, 0, raw.Length);
+            blocks.Add(ms.ToArray());
+          }
+        }
+        else blocks.Add(raw);
+      }
+      using (var o = new MemoryStream())
+      using (var w = new BinaryWriter(o))
+      {
+        w.Write(new byte[] { (byte)'P', (byte)'F', (byte)'S', (byte)'C' });
+        w.Write(0); w.Write(2); w.Write(Block); w.Write((long)Block);
+        w.Write(0x400L); w.Write(hdrSize); w.Write((long)n * Block);
+        o.Position = 0x400;
+        long off = hdrSize;
+        foreach (var b in blocks) { w.Write(off); off += b.Length; }
+        w.Write(off);
+        o.Position = hdrSize;
+        foreach (var b in blocks) w.Write(b);
+        return o.ToArray();
+      }
+    }
+
+    [TestMethod]
+    public void PfscReader_DecompressesMixedBlocksExactly()
+    {
+      // Highly compressible but non-trivial data: forces long deflate streams per block.
+      var data = new byte[40 * Block + 1234];
+      var rnd = new Random(7);
+      for (int i = 0; i < data.Length; i++)
+        data[i] = (byte)((i / 3) % 251 ^ (rnd.Next(16) == 0 ? rnd.Next(256) : 0));
+      var pfsc = MakePfsc(data, i => i % 3 != 2);
+      var reader = new PFSCReader(new TestHelper.ArrayMemoryReader(pfsc));
+      var got = new byte[data.Length];
+      reader.Read(0, got, 0, got.Length);
+      CollectionAssert.AreEqual(data, got);
+    }
+  }
+}