1 files changed, 17 insertions, 2 deletions
diff --git a/src/ProtoGen/DescriptorUtil.cs b/src/ProtoGen/DescriptorUtil.cs
index 14d28bb8..af5a2f9a 100644
--- a/src/ProtoGen/DescriptorUtil.cs
+++ b/src/ProtoGen/DescriptorUtil.cs
@@ -45,11 +45,26 @@ namespace Google.ProtocolBuffers.ProtoGen {
     internal static string GetFullUmbrellaClassName(IDescriptor descriptor) {
       CSharpFileOptions options = descriptor.File.CSharpOptions;
       string result = options.Namespace;
-      if (result != "") result += '.';
-      result += options.UmbrellaClassname;
+      if (result != "") {
+        result += '.';
+      }
+      result += GetQualifiedUmbrellaClassName(options);
       return "global::" + result;
     }
 
+    /// <summary>
+    /// Evaluates the options and returns the qualified name of the umbrella class
+    /// relative to the descriptor type's namespace.  Basically concatenates the
+    /// UmbrellaNamespace + UmbrellaClassname fields.
+    /// </summary>
+    internal static string GetQualifiedUmbrellaClassName(CSharpFileOptions options) {
+      string fullName = options.UmbrellaClassname;
+      if (!options.NestClasses && options.UmbrellaNamespace != "") {
+        fullName = String.Format("{0}.{1}", options.UmbrellaNamespace, options.UmbrellaClassname);
+      }
+      return fullName;
+    }
+
     internal static string GetMappedTypeName(MappedType type) {
       switch(type) {
         case MappedType.Int32:      return "int";