diff --git a/src/ICSharpCode.SharpZipLib/Checksum/BZip2Crc.cs b/src/ICSharpCode.SharpZipLib/Checksum/BZip2Crc.cs
index aac3075b6..9674dcec7 100644
--- a/src/ICSharpCode.SharpZipLib/Checksum/BZip2Crc.cs
+++ b/src/ICSharpCode.SharpZipLib/Checksum/BZip2Crc.cs
@@ -177,10 +177,11 @@ public void Update(byte[] buffer)
 		/// </param>
 		public void Update(ArraySegment<byte> segment)
 		{
-			foreach (byte b in segment)
-			{
-				Update(b);
-			}
+			var count = segment.Count;
+			var offset = segment.Offset;
+
+			while (--count >= 0)
+				Update(segment.Array[offset++]);
 		}
 	}
 }
diff --git a/src/ICSharpCode.SharpZipLib/Checksum/Crc32.cs b/src/ICSharpCode.SharpZipLib/Checksum/Crc32.cs
index f9861685a..9b8ab4b6d 100644
--- a/src/ICSharpCode.SharpZipLib/Checksum/Crc32.cs
+++ b/src/ICSharpCode.SharpZipLib/Checksum/Crc32.cs
@@ -166,10 +166,11 @@ public void Update(byte[] buffer)
 		/// </param>
 		public void Update(ArraySegment<byte> segment)
 		{
-			foreach (byte b in segment)
-			{
-				Update(b);
-			}
+			var count = segment.Count;
+			var offset = segment.Offset;
+
+			while (--count >= 0)
+				Update(segment.Array[offset++]);
 		}
 	}
 }
diff --git a/src/ICSharpCode.SharpZipLib/ICSharpCode.SharpZipLib.csproj b/src/ICSharpCode.SharpZipLib/ICSharpCode.SharpZipLib.csproj
index 31aabaf1c..1114826b4 100644
--- a/src/ICSharpCode.SharpZipLib/ICSharpCode.SharpZipLib.csproj
+++ b/src/ICSharpCode.SharpZipLib/ICSharpCode.SharpZipLib.csproj
@@ -17,16 +17,15 @@
     <Company>ICSharpCode</Company>
     <Authors>ICSharpCode</Authors>
     <Description>SharpZipLib (#ziplib, formerly NZipLib) is a compression library for Zip, GZip, BZip2, and Tar written entirely in C# for .NET. It is implemented as an assembly (installable in the GAC), and thus can easily be incorporated into other projects (in any .NET language)</Description>
-    <PackageLicenseUrl>https://github.com/icsharpcode/SharpZipLib/raw/master/LICENSE.txt</PackageLicenseUrl>
-    <PackageProjectUrl>http://icsharpcode.github.io/SharpZipLib/</PackageProjectUrl>
-		<iconUrl>http://icsharpcode.github.io/SharpZipLib/assets/sharpziplib-nuget-256x256.png</iconUrl>
+		<PackageLicenseExpression>MIT</PackageLicenseExpression>
+		<PackageProjectUrl>http://icsharpcode.github.io/SharpZipLib/</PackageProjectUrl>
+		<PackageIconUrl>http://icsharpcode.github.io/SharpZipLib/assets/sharpziplib-nuget-256x256.png</PackageIconUrl>
     <RepositoryUrl>https://github.com/icsharpcode/SharpZipLib</RepositoryUrl>
     <Copyright>Copyright © 2000-2018 SharpZipLib Contributors</Copyright>
     <PackageTags>Compression Library Zip GZip BZip2 LZW Tar</PackageTags>
     <NeutralLanguage>en-US</NeutralLanguage>
     <PackageReleaseNotes>
 Please see https://github.com/icsharpcode/SharpZipLib/wiki/Release-1.1 for more information.</PackageReleaseNotes>
-    <PackageLicenseUrl>https://github.com/icsharpcode/SharpZipLib/blob/master/LICENSE.txt</PackageLicenseUrl>
     <PackageProjectUrl>https://github.com/icsharpcode/SharpZipLib</PackageProjectUrl> 
   </PropertyGroup>
 
diff --git a/src/ICSharpCode.SharpZipLib/Zip/ZipFile.cs b/src/ICSharpCode.SharpZipLib/Zip/ZipFile.cs
index 778abfd15..fa4c09401 100644
--- a/src/ICSharpCode.SharpZipLib/Zip/ZipFile.cs
+++ b/src/ICSharpCode.SharpZipLib/Zip/ZipFile.cs
@@ -2461,7 +2461,9 @@ private void CopyEntryDataDirect(ZipUpdate update, Stream stream, bool updateCrc
 		private int FindExistingUpdate(ZipEntry entry)
 		{
 			int result = -1;
-			string convertedName = GetTransformedFileName(entry.Name);
+			string convertedName = entry.IsDirectory
+				? GetTransformedDirectoryName(entry.Name)
+				: GetTransformedFileName(entry.Name);
 
 			if (updateIndex_.ContainsKey(convertedName))
 			{
diff --git a/test/ICSharpCode.SharpZipLib.Tests/Zip/ZipFileHandling.cs b/test/ICSharpCode.SharpZipLib.Tests/Zip/ZipFileHandling.cs
index 9496938e8..6cbcfd824 100644
--- a/test/ICSharpCode.SharpZipLib.Tests/Zip/ZipFileHandling.cs
+++ b/test/ICSharpCode.SharpZipLib.Tests/Zip/ZipFileHandling.cs
@@ -403,6 +403,8 @@ public void AddAndDeleteEntries()
 			string addFile2 = Path.Combine(tempFile, "b.dat");
 			MakeTempFile(addFile2, 259);
 
+			string addDirectory = Path.Combine(tempFile, "dir");
+
 			tempFile = Path.Combine(tempFile, "SharpZipTest.Zip");
 
 			using (ZipFile f = ZipFile.Create(tempFile))
@@ -410,17 +412,27 @@ public void AddAndDeleteEntries()
 				f.BeginUpdate();
 				f.Add(addFile);
 				f.Add(addFile2);
+				f.AddDirectory(addDirectory);
 				f.CommitUpdate();
 				Assert.IsTrue(f.TestArchive(true));
 			}
 
 			using (ZipFile f = new ZipFile(tempFile))
 			{
-				Assert.AreEqual(2, f.Count);
+				Assert.AreEqual(3, f.Count);
 				Assert.IsTrue(f.TestArchive(true));
+
+				// Delete file
 				f.BeginUpdate();
 				f.Delete(f[0]);
 				f.CommitUpdate();
+				Assert.AreEqual(2, f.Count);
+				Assert.IsTrue(f.TestArchive(true));
+
+				// Delete directory
+				f.BeginUpdate();
+				f.Delete(f[1]);
+				f.CommitUpdate();
 				Assert.AreEqual(1, f.Count);
 				Assert.IsTrue(f.TestArchive(true));
 			}