diff --git a/src/ICSharpCode.SharpZipLib/Zip/ZipFile.cs b/src/ICSharpCode.SharpZipLib/Zip/ZipFile.cs
index 1e9bf43d3..b34b7bec5 100644
--- a/src/ICSharpCode.SharpZipLib/Zip/ZipFile.cs
+++ b/src/ICSharpCode.SharpZipLib/Zip/ZipFile.cs
@@ -1145,12 +1145,12 @@ private long TestLocalHeader(ZipEntry entry, HeaderTest tests)
 					if (localFlags.HasAny(GeneralBitFlags.Descriptor))
 					{
 						// These may be valid if patched later
-						if ((size > 0) && (size != entry.Size))
+						if ((size != 0) && (size != entry.Size))
 						{
 							throw new ZipException("Size invalid for descriptor");
 						}
 
-						if ((compressedSize > 0) && (compressedSize != entry.CompressedSize))
+						if ((compressedSize != 0) && (compressedSize != entry.CompressedSize))
 						{
 							throw new ZipException("Compressed size invalid for descriptor");
 						}
diff --git a/src/ICSharpCode.SharpZipLib/Zip/ZipFormat.cs b/src/ICSharpCode.SharpZipLib/Zip/ZipFormat.cs
index a37ab3031..cf78ef54f 100644
--- a/src/ICSharpCode.SharpZipLib/Zip/ZipFormat.cs
+++ b/src/ICSharpCode.SharpZipLib/Zip/ZipFormat.cs
@@ -114,8 +114,9 @@ internal static int WriteLocalHeader(Stream stream, ZipEntry entry, out EntryPat
 				}
 				else
 				{
-					ed.AddLeLong(-1);
-					ed.AddLeLong(-1);
+					// If the sizes are stored in the descriptor, the local Zip64 sizes should be 0
+					ed.AddLeLong(0);
+					ed.AddLeLong(0);
 				}
 				ed.AddNewEntry(1);