1 files changed, 5 insertions, 1 deletions
diff --git a/src/google/protobuf/util/internal/proto_writer.cc b/src/google/protobuf/util/internal/proto_writer.cc
index 18cc1233..3e09c9bb 100644
--- a/src/google/protobuf/util/internal/proto_writer.cc
+++ b/src/google/protobuf/util/internal/proto_writer.cc
@@ -71,6 +71,7 @@ ProtoWriter::ProtoWriter(TypeResolver* type_resolver,
       adapter_(&buffer_),
       stream_(new CodedOutputStream(&adapter_)),
       listener_(listener),
+      ignore_unknown_fields_(false),
       invalid_depth_(0),
       tracker_(new ObjectLocationTracker()) {}
 
@@ -88,6 +89,7 @@ ProtoWriter::ProtoWriter(const TypeInfo* typeinfo,
       adapter_(&buffer_),
       stream_(new CodedOutputStream(&adapter_)),
       listener_(listener),
+      ignore_unknown_fields_(false),
       invalid_depth_(0),
       tracker_(new ObjectLocationTracker()) {}
 
@@ -702,7 +704,9 @@ const google::protobuf::Field* ProtoWriter::Lookup(
   }
   const google::protobuf::Field* field =
       typeinfo_->FindField(&e->type(), unnormalized_name);
-  if (field == NULL) InvalidName(unnormalized_name, "Cannot find field.");
+  if (field == NULL && !ignore_unknown_fields_) {
+    InvalidName(unnormalized_name, "Cannot find field.");
+  }
   return field;
 }