2 files changed, 8 insertions, 0 deletions
diff --git a/src/ProtocolBuffers/AbstractBuilder.cs b/src/ProtocolBuffers/AbstractBuilder.cs
index d613eca4..0d1279c7 100644
--- a/src/ProtocolBuffers/AbstractBuilder.cs
+++ b/src/ProtocolBuffers/AbstractBuilder.cs
@@ -129,6 +129,10 @@ namespace Google.ProtocolBuffers {
           this[field] = entry.Value;
         }
       }
+
+      //Fix for unknown fields not merging, see java's AbstractMessage.Builder<T> line 236
+      MergeUnknownFields(other.UnknownFields);
+
       return ThisBuilder;
     }
 
diff --git a/src/ProtocolBuffers/GeneratedBuilder.cs b/src/ProtocolBuffers/GeneratedBuilder.cs
index 01d3d2dd..2ec2762f 100644
--- a/src/ProtocolBuffers/GeneratedBuilder.cs
+++ b/src/ProtocolBuffers/GeneratedBuilder.cs
@@ -158,6 +158,10 @@ namespace Google.ProtocolBuffers {
           this[field] = entry.Value;
         }
       }
+
+      //Fix for unknown fields not merging, see java's AbstractMessage.Builder<T> line 236
+      MergeUnknownFields(other.UnknownFields);
+
       return ThisBuilder;
     }