diff --git a/src/Core/Authoring/PackageBuilder.cs b/src/Core/Authoring/PackageBuilder.cs
index afa5991be..d3aeb09a2 100644
--- a/src/Core/Authoring/PackageBuilder.cs
+++ b/src/Core/Authoring/PackageBuilder.cs
@@ -259,7 +259,7 @@ public void Save(Stream stream)
                 WriteManifest(package, DetermineMinimumSchemaVersion(Files, DependencySets));
 
                 // Write the files to the package
-                WriteFiles(package);
+                WriteFiles(package, Id);
 
                 // Copy the metadata properties back to the package
                 package.PackageProperties.Creator = String.Join(",", Authors);
@@ -484,7 +484,7 @@ private void WriteManifest(Package package, int minimumManifestVersion)
             }
         }
 
-        private void WriteFiles(Package package)
+        private void WriteFiles(Package package, string packageId)
         {
             // Add files that might not come from expanding files on disk
             foreach (IPackageFile file in new HashSet<IPackageFile>(Files))
@@ -493,7 +493,7 @@ private void WriteFiles(Package package)
                 {
                     try
                     {
-                        CreatePart(package, file.Path, stream);
+                        CreatePart(package, file.Path, stream, packageId);
                     }
                     catch
                     {
@@ -592,9 +592,9 @@ private static void ExcludeFiles(List<PhysicalPackageFile> searchFiles, string b
             }
         }
 
-        private static void CreatePart(Package package, string path, Stream sourceStream)
+        private static void CreatePart(Package package, string path, Stream sourceStream, string packageId)
         {
-            if (PackageHelper.IsPackageManifest(path, package.PackageProperties.Identifier))
+            if (PackageHelper.IsPackageManifest(path, packageId))
             {
                 return;
             }
diff --git a/src/Core/Packages/OptimizedZipPackage.cs b/src/Core/Packages/OptimizedZipPackage.cs
index fa9b20c46..4fb86058d 100644
--- a/src/Core/Packages/OptimizedZipPackage.cs
+++ b/src/Core/Packages/OptimizedZipPackage.cs
@@ -254,7 +254,7 @@ private void EnsurePackageFiles()
                 Package package = Package.Open(stream);
                 // unzip files inside package
                 var files = from part in package.GetParts()
-                            where ZipPackage.IsPackageFile(part, package.PackageProperties.Identifier)
+                            where ZipPackage.IsPackageFile(part, Id)
                             select part;
 
                 // now copy all package's files to disk