diff --git a/jsonpb/jsonpb.go b/jsonpb/jsonpb.go
index d1f6f28..768564e 100644
--- a/jsonpb/jsonpb.go
+++ b/jsonpb/jsonpb.go
@@ -41,6 +41,7 @@
 import (
 	"bytes"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"io"
 	"reflect"
@@ -125,6 +126,10 @@
 			out.write(x)
 			out.write(`s"`)
 			return out.err
+		case "Struct":
+			// Let marshalValue handle the `fields` map.
+			// TODO: pass the correct Properties if needed.
+			return m.marshalValue(out, &proto.Properties{}, s.Field(0), indent)
 		case "Timestamp":
 			// "RFC 3339, where generated output will always be Z-normalized
 			//  and uses 3, 6 or 9 fractional digits."
@@ -138,6 +143,17 @@
 			out.write(x)
 			out.write(`Z"`)
 			return out.err
+		case "Value":
+			// Value has a single oneof.
+			kind := s.Field(0)
+			if kind.IsNil() {
+				// "absence of any variant indicates an error"
+				return errors.New("nil Value")
+			}
+			// oneof -> *T -> T -> T.F
+			x := kind.Elem().Elem().Field(0)
+			// TODO: pass the correct Properties if needed.
+			return m.marshalValue(out, &proto.Properties{}, x, indent)
 		}
 	}
 
@@ -304,6 +320,19 @@
 		return out.err
 	}
 
+	// Handle well-known types.
+	// Most are handled up in marshalObject (because 99% are messages).
+	type wkt interface {
+		XXX_WellKnownType() string
+	}
+	if wkt, ok := v.Interface().(wkt); ok {
+		switch wkt.XXX_WellKnownType() {
+		case "NullValue":
+			out.write("null")
+			return out.err
+		}
+	}
+
 	// Handle enumerations.
 	if !m.EnumsAsInts && prop.Enum != "" {
 		// Unknown enum values will are stringified by the proto library as their
diff --git a/jsonpb/jsonpb_test.go b/jsonpb/jsonpb_test.go
index a970063..3d70b87 100644
--- a/jsonpb/jsonpb_test.go
+++ b/jsonpb/jsonpb_test.go
@@ -40,6 +40,7 @@
 	pb "github.com/golang/protobuf/jsonpb/jsonpb_test_proto"
 	proto3pb "github.com/golang/protobuf/proto/proto3_proto"
 	durpb "github.com/golang/protobuf/ptypes/duration"
+	stpb "github.com/golang/protobuf/ptypes/struct"
 	tspb "github.com/golang/protobuf/ptypes/timestamp"
 	wpb "github.com/golang/protobuf/ptypes/wrappers"
 )
@@ -321,6 +322,12 @@
 	{"proto2 extension", marshaler, realNumber, realNumberJSON},
 
 	{"Duration", marshaler, &pb.KnownTypes{Dur: &durpb.Duration{Seconds: 3}}, `{"dur":"3.000s"}`},
+	{"Struct", marshaler, &pb.KnownTypes{St: &stpb.Struct{
+		Fields: map[string]*stpb.Value{
+			"one": &stpb.Value{Kind: &stpb.Value_StringValue{"loneliest number"}},
+			"two": &stpb.Value{Kind: &stpb.Value_NullValue{stpb.NullValue_NULL_VALUE}},
+		},
+	}}, `{"st":{"one":"loneliest number","two":null}}`},
 	{"Timestamp", marshaler, &pb.KnownTypes{Ts: &tspb.Timestamp{Seconds: 14e8, Nanos: 21e6}}, `{"ts":"2014-05-13T16:53:20.021Z"}`},
 
 	{"DoubleValue", marshaler, &pb.KnownTypes{Dbl: &wpb.DoubleValue{Value: 1.2}}, `{"dbl":1.2}`},
diff --git a/jsonpb/jsonpb_test_proto/Makefile b/jsonpb/jsonpb_test_proto/Makefile
index d6e9768..3f845ba 100644
--- a/jsonpb/jsonpb_test_proto/Makefile
+++ b/jsonpb/jsonpb_test_proto/Makefile
@@ -30,4 +30,4 @@
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 regenerate:
-	protoc --go_out=Mgoogle/protobuf/duration.proto=github.com/golang/protobuf/ptypes/duration,Mgoogle/protobuf/timestamp.proto=github.com/golang/protobuf/ptypes/timestamp,Mgoogle/protobuf/wrappers.proto=github.com/golang/protobuf/ptypes/wrappers:. *.proto
+	protoc --go_out=Mgoogle/protobuf/duration.proto=github.com/golang/protobuf/ptypes/duration,Mgoogle/protobuf/struct.proto=github.com/golang/protobuf/ptypes/struct,Mgoogle/protobuf/timestamp.proto=github.com/golang/protobuf/ptypes/timestamp,Mgoogle/protobuf/wrappers.proto=github.com/golang/protobuf/ptypes/wrappers:. *.proto
diff --git a/jsonpb/jsonpb_test_proto/test_objects.pb.go b/jsonpb/jsonpb_test_proto/test_objects.pb.go
index de58e89..a1263fb 100644
--- a/jsonpb/jsonpb_test_proto/test_objects.pb.go
+++ b/jsonpb/jsonpb_test_proto/test_objects.pb.go
@@ -8,8 +8,9 @@
 import fmt "fmt"
 import math "math"
 import google_protobuf "github.com/golang/protobuf/ptypes/duration"
-import google_protobuf1 "github.com/golang/protobuf/ptypes/timestamp"
-import google_protobuf2 "github.com/golang/protobuf/ptypes/wrappers"
+import google_protobuf1 "github.com/golang/protobuf/ptypes/struct"
+import google_protobuf2 "github.com/golang/protobuf/ptypes/timestamp"
+import google_protobuf3 "github.com/golang/protobuf/ptypes/wrappers"
 
 // Reference imports to suppress errors if they are not otherwise used.
 var _ = proto.Marshal
@@ -519,16 +520,17 @@
 
 type KnownTypes struct {
 	Dur              *google_protobuf.Duration     `protobuf:"bytes,1,opt,name=dur" json:"dur,omitempty"`
-	Ts               *google_protobuf1.Timestamp   `protobuf:"bytes,2,opt,name=ts" json:"ts,omitempty"`
-	Dbl              *google_protobuf2.DoubleValue `protobuf:"bytes,3,opt,name=dbl" json:"dbl,omitempty"`
-	Flt              *google_protobuf2.FloatValue  `protobuf:"bytes,4,opt,name=flt" json:"flt,omitempty"`
-	I64              *google_protobuf2.Int64Value  `protobuf:"bytes,5,opt,name=i64" json:"i64,omitempty"`
-	U64              *google_protobuf2.UInt64Value `protobuf:"bytes,6,opt,name=u64" json:"u64,omitempty"`
-	I32              *google_protobuf2.Int32Value  `protobuf:"bytes,7,opt,name=i32" json:"i32,omitempty"`
-	U32              *google_protobuf2.UInt32Value `protobuf:"bytes,8,opt,name=u32" json:"u32,omitempty"`
-	Bool             *google_protobuf2.BoolValue   `protobuf:"bytes,9,opt,name=bool" json:"bool,omitempty"`
-	Str              *google_protobuf2.StringValue `protobuf:"bytes,10,opt,name=str" json:"str,omitempty"`
-	Bytes            *google_protobuf2.BytesValue  `protobuf:"bytes,11,opt,name=bytes" json:"bytes,omitempty"`
+	St               *google_protobuf1.Struct      `protobuf:"bytes,12,opt,name=st" json:"st,omitempty"`
+	Ts               *google_protobuf2.Timestamp   `protobuf:"bytes,2,opt,name=ts" json:"ts,omitempty"`
+	Dbl              *google_protobuf3.DoubleValue `protobuf:"bytes,3,opt,name=dbl" json:"dbl,omitempty"`
+	Flt              *google_protobuf3.FloatValue  `protobuf:"bytes,4,opt,name=flt" json:"flt,omitempty"`
+	I64              *google_protobuf3.Int64Value  `protobuf:"bytes,5,opt,name=i64" json:"i64,omitempty"`
+	U64              *google_protobuf3.UInt64Value `protobuf:"bytes,6,opt,name=u64" json:"u64,omitempty"`
+	I32              *google_protobuf3.Int32Value  `protobuf:"bytes,7,opt,name=i32" json:"i32,omitempty"`
+	U32              *google_protobuf3.UInt32Value `protobuf:"bytes,8,opt,name=u32" json:"u32,omitempty"`
+	Bool             *google_protobuf3.BoolValue   `protobuf:"bytes,9,opt,name=bool" json:"bool,omitempty"`
+	Str              *google_protobuf3.StringValue `protobuf:"bytes,10,opt,name=str" json:"str,omitempty"`
+	Bytes            *google_protobuf3.BytesValue  `protobuf:"bytes,11,opt,name=bytes" json:"bytes,omitempty"`
 	XXX_unrecognized []byte                        `json:"-"`
 }
 
@@ -544,70 +546,77 @@
 	return nil
 }
 
-func (m *KnownTypes) GetTs() *google_protobuf1.Timestamp {
+func (m *KnownTypes) GetSt() *google_protobuf1.Struct {
+	if m != nil {
+		return m.St
+	}
+	return nil
+}
+
+func (m *KnownTypes) GetTs() *google_protobuf2.Timestamp {
 	if m != nil {
 		return m.Ts
 	}
 	return nil
 }
 
-func (m *KnownTypes) GetDbl() *google_protobuf2.DoubleValue {
+func (m *KnownTypes) GetDbl() *google_protobuf3.DoubleValue {
 	if m != nil {
 		return m.Dbl
 	}
 	return nil
 }
 
-func (m *KnownTypes) GetFlt() *google_protobuf2.FloatValue {
+func (m *KnownTypes) GetFlt() *google_protobuf3.FloatValue {
 	if m != nil {
 		return m.Flt
 	}
 	return nil
 }
 
-func (m *KnownTypes) GetI64() *google_protobuf2.Int64Value {
+func (m *KnownTypes) GetI64() *google_protobuf3.Int64Value {
 	if m != nil {
 		return m.I64
 	}
 	return nil
 }
 
-func (m *KnownTypes) GetU64() *google_protobuf2.UInt64Value {
+func (m *KnownTypes) GetU64() *google_protobuf3.UInt64Value {
 	if m != nil {
 		return m.U64
 	}
 	return nil
 }
 
-func (m *KnownTypes) GetI32() *google_protobuf2.Int32Value {
+func (m *KnownTypes) GetI32() *google_protobuf3.Int32Value {
 	if m != nil {
 		return m.I32
 	}
 	return nil
 }
 
-func (m *KnownTypes) GetU32() *google_protobuf2.UInt32Value {
+func (m *KnownTypes) GetU32() *google_protobuf3.UInt32Value {
 	if m != nil {
 		return m.U32
 	}
 	return nil
 }
 
-func (m *KnownTypes) GetBool() *google_protobuf2.BoolValue {
+func (m *KnownTypes) GetBool() *google_protobuf3.BoolValue {
 	if m != nil {
 		return m.Bool
 	}
 	return nil
 }
 
-func (m *KnownTypes) GetStr() *google_protobuf2.StringValue {
+func (m *KnownTypes) GetStr() *google_protobuf3.StringValue {
 	if m != nil {
 		return m.Str
 	}
 	return nil
 }
 
-func (m *KnownTypes) GetBytes() *google_protobuf2.BytesValue {
+func (m *KnownTypes) GetBytes() *google_protobuf3.BytesValue {
 	if m != nil {
 		return m.Bytes
 	}
@@ -637,65 +646,66 @@
 }
 
 var fileDescriptor1 = []byte{
-	// 947 bytes of a gzipped FileDescriptorProto
-	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x09, 0x6e, 0x88, 0x02, 0xff, 0x7c, 0x95, 0xd1, 0x72, 0xdb, 0x44,
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-	0x08, 0x00, 0x00,
+	// 973 bytes of a gzipped FileDescriptorProto
+	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x09, 0x6e, 0x88, 0x02, 0xff, 0x7c, 0x55, 0xdd, 0x72, 0xdb, 0x44,
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+	0x5e, 0x7a, 0xe4, 0x44, 0x31, 0x2a, 0x92, 0x56, 0xb3, 0x5a, 0x91, 0x7a, 0xe0, 0x82, 0x87, 0xe0,
+	0x15, 0xe0, 0x11, 0xb8, 0xe4, 0xd9, 0x38, 0x67, 0x57, 0xd2, 0x3a, 0x76, 0x4d, 0x6e, 0xe2, 0xa3,
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+	0x06, 0x25, 0x6d, 0x50, 0x04, 0x83, 0x92, 0xa7, 0x2b, 0xaa, 0x2e, 0x28, 0x82, 0x41, 0x49, 0x1b,
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+	0xb4, 0x41, 0x11, 0x0c, 0x4a, 0xda, 0xa0, 0x64, 0x17, 0x14, 0xc1, 0xa0, 0xa4, 0x09, 0xea, 0x1f,
+	0x68, 0xa8, 0x17, 0xe9, 0xc5, 0x22, 0x51, 0xec, 0x1e, 0x75, 0xcf, 0x45, 0x26, 0xa4, 0xee, 0xa7,
+	0xbd, 0xc9, 0x7e, 0x64, 0x5a, 0x3e, 0x32, 0x70, 0xf4, 0x04, 0x31, 0x6e, 0x28, 0xec, 0x33, 0xf4,
+	0x33, 0x6c, 0x0c, 0x6f, 0x1b, 0x7b, 0x20, 0xf5, 0x7f, 0x76, 0x97, 0x0e, 0x2a, 0xdd, 0xb5, 0x7a,
+	0x03, 0x87, 0x93, 0xbd, 0x96, 0x6d, 0x7a, 0x99, 0x37, 0x28, 0xfb, 0xd8, 0x04, 0xa2, 0x99, 0xb8,
+	0xce, 0x4d, 0x26, 0x06, 0xd4, 0x50, 0x3d, 0x69, 0x36, 0x38, 0xdc, 0xd7, 0x9e, 0x6f, 0xb4, 0xcc,
+	0x66, 0xdf, 0x79, 0x8b, 0xb3, 0x4f, 0x69, 0x20, 0x67, 0x2d, 0xf9, 0xa6, 0xb6, 0xdd, 0x20, 0xfb,
+	0xb2, 0xf9, 0x35, 0xfe, 0x80, 0xba, 0x66, 0xd1, 0x1e, 0x25, 0x7c, 0x7a, 0x3c, 0xba, 0xc1, 0x02,
+	0xea, 0x7e, 0xcb, 0xa7, 0xd3, 0x67, 0xa3, 0x1e, 0xf3, 0x69, 0xff, 0xe8, 0x87, 0xb3, 0xe9, 0xc8,
+	0x19, 0xff, 0xe9, 0xd0, 0xfe, 0x49, 0x5c, 0x56, 0xec, 0x4b, 0x3a, 0xcc, 0x4d, 0xbb, 0x60, 0xf6,
+	0xba, 0xc7, 0x86, 0x93, 0xb7, 0x5b, 0x7f, 0xa4, 0x44, 0x27, 0xba, 0x7f, 0x60, 0x2b, 0xa6, 0x85,
+	0x92, 0x4b, 0x1e, 0xe4, 0x6d, 0xcd, 0xbe, 0xa6, 0xbb, 0xb9, 0xee, 0xcd, 0xf6, 0xab, 0x1d, 0x2d,
+	0x7f, 0xe7, 0xba, 0x1c, 0xfb, 0xd5, 0x7c, 0xb6, 0x31, 0x18, 0xe6, 0xf6, 0xc9, 0xc1, 0x57, 0x74,
+	0xef, 0xba, 0x3f, 0x1b, 0x51, 0xf2, 0x4b, 0xb2, 0xd4, 0xdb, 0x48, 0x38, 0xfe, 0x64, 0xfb, 0xd4,
+	0xfd, 0x35, 0xce, 0xea, 0x44, 0x8f, 0x84, 0x80, 0x9b, 0xe2, 0xb1, 0xf3, 0x45, 0xef, 0xe0, 0x19,
+	0x1d, 0xad, 0xdb, 0xaf, 0xea, 0x7d, 0xa3, 0x7f, 0x7f, 0x55, 0xbf, 0xb9, 0x29, 0xd6, 0x6f, 0xfc,
+	0x94, 0xee, 0x9c, 0x54, 0x8b, 0x17, 0xa9, 0xfa, 0xf9, 0xc7, 0x22, 0x11, 0x97, 0xec, 0x2d, 0xea,
+	0xaa, 0x54, 0xc1, 0x87, 0xa1, 0x5b, 0xf0, 0xdd, 0x0d, 0x6e, 0x4a, 0x16, 0x42, 0x47, 0xc4, 0x59,
+	0x2c, 0x97, 0xda, 0x92, 0x00, 0xd0, 0xd4, 0x47, 0x1e, 0x75, 0xeb, 0x02, 0x06, 0xea, 0xf8, 0x2e,
+	0xed, 0xf3, 0x24, 0xce, 0xec, 0xe2, 0x7b, 0x7a, 0x2e, 0x98, 0xe2, 0x9e, 0xef, 0x5f, 0x8c, 0xfe,
+	0x80, 0x3f, 0x67, 0x7c, 0x45, 0xbd, 0x27, 0x02, 0xd7, 0xf1, 0x8a, 0x1d, 0xd2, 0x20, 0xcd, 0xe3,
+	0x45, 0x5a, 0xa0, 0xb1, 0xa1, 0xdb, 0x07, 0x56, 0x32, 0x39, 0xa6, 0x7b, 0x12, 0xac, 0x67, 0xc9,
+	0x2b, 0x95, 0x14, 0x15, 0xbc, 0x8c, 0xed, 0xd8, 0x86, 0x88, 0xb3, 0xf0, 0xb7, 0xeb, 0x1d, 0xd5,
+	0xd8, 0xf3, 0x5d, 0x14, 0x4d, 0x5b, 0xcd, 0xf8, 0xdf, 0x3e, 0xa5, 0xdf, 0x17, 0xe2, 0xaa, 0x78,
+	0xbe, 0x2c, 0x93, 0x8a, 0x7d, 0x42, 0x09, 0x5c, 0x06, 0xfa, 0xb5, 0xc3, 0xc9, 0xed, 0xc8, 0x4c,
+	0xf2, 0xa8, 0x9d, 0xe4, 0xd1, 0x71, 0x73, 0x51, 0x70, 0x64, 0xb1, 0x0f, 0xa9, 0x53, 0xa9, 0x70,
+	0x47, 0x73, 0x6f, 0x6d, 0x70, 0x4f, 0xf5, 0xa5, 0xc1, 0x81, 0x02, 0xa7, 0xd2, 0x81, 0xae, 0x35,
+	0xb9, 0x1f, 0x6c, 0x10, 0x9f, 0xb7, 0xf7, 0x07, 0x07, 0x16, 0x8b, 0x60, 0x05, 0xf3, 0x4c, 0x8f,
+	0xf7, 0xe1, 0xe4, 0x70, 0x73, 0x05, 0x7a, 0x4c, 0xfc, 0x84, 0xf1, 0x71, 0x24, 0xc2, 0x29, 0x26,
+	0x97, 0x99, 0xd2, 0x43, 0x1f, 0x5b, 0x76, 0x9d, 0xaf, 0x07, 0x4e, 0x43, 0x07, 0x1e, 0xd2, 0xd3,
+	0xe6, 0x22, 0x78, 0x1d, 0x5d, 0x37, 0x61, 0x43, 0x07, 0x1e, 0xae, 0xa6, 0x06, 0xfa, 0x60, 0xcb,
+	0x6a, 0xce, 0x56, 0xf9, 0x40, 0xd4, 0xf6, 0x30, 0x23, 0xbd, 0xed, 0xf6, 0x0f, 0x26, 0xad, 0x3d,
+	0x0c, 0x4f, 0xb4, 0x07, 0xba, 0xff, 0x3f, 0xf6, 0x1d, 0xbf, 0xd6, 0xfc, 0xbe, 0xbe, 0x04, 0x82,
+	0x2d, 0x51, 0xe2, 0x29, 0x30, 0x74, 0xcd, 0x43, 0x7f, 0x3c, 0xcf, 0x74, 0x8b, 0xbf, 0x19, 0xac,
+	0x8d, 0x3f, 0x10, 0xd9, 0xe7, 0xd4, 0xb5, 0x37, 0xd1, 0xeb, 0x3e, 0x40, 0x0f, 0x5c, 0x23, 0x30,
+	0xcc, 0xc7, 0x77, 0x68, 0xbf, 0x88, 0xf3, 0x64, 0xad, 0xf9, 0x7e, 0xd7, 0x67, 0x54, 0x23, 0xff,
+	0x05, 0x00, 0x00, 0xff, 0xff, 0x87, 0xe6, 0xa7, 0x10, 0x8b, 0x08, 0x00, 0x00,
 }
diff --git a/jsonpb/jsonpb_test_proto/test_objects.proto b/jsonpb/jsonpb_test_proto/test_objects.proto
index 394c424..4346935 100644
--- a/jsonpb/jsonpb_test_proto/test_objects.proto
+++ b/jsonpb/jsonpb_test_proto/test_objects.proto
@@ -32,6 +32,7 @@
 syntax = "proto2";
 
 import "google/protobuf/duration.proto";
+import "google/protobuf/struct.proto";
 import "google/protobuf/timestamp.proto";
 import "google/protobuf/wrappers.proto";
 
@@ -115,6 +116,7 @@
 
 message KnownTypes {
   optional google.protobuf.Duration dur = 1;
+  optional google.protobuf.Struct st = 12;
   optional google.protobuf.Timestamp ts = 2;
 
   optional google.protobuf.DoubleValue dbl = 3;