diff --git a/jsonpb/jsonpb.go b/jsonpb/jsonpb.go
index e40d1d3..38f86c5 100644
--- a/jsonpb/jsonpb.go
+++ b/jsonpb/jsonpb.go
@@ -812,10 +812,21 @@
 // The easiest way to sort them in some deterministic order is to use fmt.
 // If this turns out to be inefficient we can always consider other options,
 // such as doing a Schwartzian transform.
+//
+// Numeric keys are sorted in numeric order per
+// https://developers.google.com/protocol-buffers/docs/proto#maps.
 type mapKeys []reflect.Value
 
 func (s mapKeys) Len() int      { return len(s) }
 func (s mapKeys) Swap(i, j int) { s[i], s[j] = s[j], s[i] }
 func (s mapKeys) Less(i, j int) bool {
+	if k := s[i].Kind(); k == s[j].Kind() {
+		switch k {
+		case reflect.Int32, reflect.Int64:
+			return s[i].Int() < s[j].Int()
+		case reflect.Uint32, reflect.Uint64:
+			return s[i].Uint() < s[j].Uint()
+		}
+	}
 	return fmt.Sprint(s[i].Interface()) < fmt.Sprint(s[j].Interface())
 }
diff --git a/jsonpb/jsonpb_test.go b/jsonpb/jsonpb_test.go
index 8cbc8ec..b4507e7 100644
--- a/jsonpb/jsonpb_test.go
+++ b/jsonpb/jsonpb_test.go
@@ -365,6 +365,10 @@
 	// TODO: This is broken.
 	//{"map<string, enum>", marshaler, &pb.Mappy{Enumy: map[string]pb.Numeral{"XIV": pb.Numeral_ROMAN}}, `{"enumy":{"XIV":"ROMAN"}`},
 	{"map<string, enum as int>", Marshaler{EnumsAsInts: true}, &pb.Mappy{Enumy: map[string]pb.Numeral{"XIV": pb.Numeral_ROMAN}}, `{"enumy":{"XIV":2}}`},
+	{"map<int32, bool>", marshaler, &pb.Mappy{S32Booly: map[int32]bool{1: true, 3: false, 10: true, 12: false}}, `{"s32booly":{"1":true,"3":false,"10":true,"12":false}}`},
+	{"map<int64, bool>", marshaler, &pb.Mappy{S64Booly: map[int64]bool{1: true, 3: false, 10: true, 12: false}}, `{"s64booly":{"1":true,"3":false,"10":true,"12":false}}`},
+	{"map<uint32, bool>", marshaler, &pb.Mappy{U32Booly: map[uint32]bool{1: true, 3: false, 10: true, 12: false}}, `{"u32booly":{"1":true,"3":false,"10":true,"12":false}}`},
+	{"map<uint64, bool>", marshaler, &pb.Mappy{U64Booly: map[uint64]bool{1: true, 3: false, 10: true, 12: false}}, `{"u64booly":{"1":true,"3":false,"10":true,"12":false}}`},
 	{"proto2 map<int64, string>", marshaler, &pb.Maps{MInt64Str: map[int64]string{213: "cat"}},
 		`{"mInt64Str":{"213":"cat"}}`},
 	{"proto2 map<bool, Object>", marshaler,
diff --git a/jsonpb/jsonpb_test_proto/more_test_objects.pb.go b/jsonpb/jsonpb_test_proto/more_test_objects.pb.go
index a5444a2..101db7a 100644
--- a/jsonpb/jsonpb_test_proto/more_test_objects.pb.go
+++ b/jsonpb/jsonpb_test_proto/more_test_objects.pb.go
@@ -72,12 +72,16 @@
 func (*Simple3) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{0} }
 
 type Mappy struct {
-	Nummy map[int64]int32    `protobuf:"bytes,1,rep,name=nummy" json:"nummy,omitempty" protobuf_key:"varint,1,opt,name=key" protobuf_val:"varint,2,opt,name=value"`
-	Strry map[string]string  `protobuf:"bytes,2,rep,name=strry" json:"strry,omitempty" protobuf_key:"bytes,1,opt,name=key" protobuf_val:"bytes,2,opt,name=value"`
-	Objjy map[int32]*Simple3 `protobuf:"bytes,3,rep,name=objjy" json:"objjy,omitempty" protobuf_key:"varint,1,opt,name=key" protobuf_val:"bytes,2,opt,name=value"`
-	Buggy map[int64]string   `protobuf:"bytes,4,rep,name=buggy" json:"buggy,omitempty" protobuf_key:"varint,1,opt,name=key" protobuf_val:"bytes,2,opt,name=value"`
-	Booly map[bool]bool      `protobuf:"bytes,5,rep,name=booly" json:"booly,omitempty" protobuf_key:"varint,1,opt,name=key" protobuf_val:"varint,2,opt,name=value"`
-	Enumy map[string]Numeral `protobuf:"bytes,6,rep,name=enumy" json:"enumy,omitempty" protobuf_key:"bytes,1,opt,name=key" protobuf_val:"varint,2,opt,name=value,enum=jsonpb.Numeral"`
+	Nummy    map[int64]int32    `protobuf:"bytes,1,rep,name=nummy" json:"nummy,omitempty" protobuf_key:"varint,1,opt,name=key" protobuf_val:"varint,2,opt,name=value"`
+	Strry    map[string]string  `protobuf:"bytes,2,rep,name=strry" json:"strry,omitempty" protobuf_key:"bytes,1,opt,name=key" protobuf_val:"bytes,2,opt,name=value"`
+	Objjy    map[int32]*Simple3 `protobuf:"bytes,3,rep,name=objjy" json:"objjy,omitempty" protobuf_key:"varint,1,opt,name=key" protobuf_val:"bytes,2,opt,name=value"`
+	Buggy    map[int64]string   `protobuf:"bytes,4,rep,name=buggy" json:"buggy,omitempty" protobuf_key:"varint,1,opt,name=key" protobuf_val:"bytes,2,opt,name=value"`
+	Booly    map[bool]bool      `protobuf:"bytes,5,rep,name=booly" json:"booly,omitempty" protobuf_key:"varint,1,opt,name=key" protobuf_val:"varint,2,opt,name=value"`
+	Enumy    map[string]Numeral `protobuf:"bytes,6,rep,name=enumy" json:"enumy,omitempty" protobuf_key:"bytes,1,opt,name=key" protobuf_val:"varint,2,opt,name=value,enum=jsonpb.Numeral"`
+	S32Booly map[int32]bool     `protobuf:"bytes,7,rep,name=s32booly" json:"s32booly,omitempty" protobuf_key:"varint,1,opt,name=key" protobuf_val:"varint,2,opt,name=value"`
+	S64Booly map[int64]bool     `protobuf:"bytes,8,rep,name=s64booly" json:"s64booly,omitempty" protobuf_key:"varint,1,opt,name=key" protobuf_val:"varint,2,opt,name=value"`
+	U32Booly map[uint32]bool    `protobuf:"bytes,9,rep,name=u32booly" json:"u32booly,omitempty" protobuf_key:"varint,1,opt,name=key" protobuf_val:"varint,2,opt,name=value"`
+	U64Booly map[uint64]bool    `protobuf:"bytes,10,rep,name=u64booly" json:"u64booly,omitempty" protobuf_key:"varint,1,opt,name=key" protobuf_val:"varint,2,opt,name=value"`
 }
 
 func (m *Mappy) Reset()                    { *m = Mappy{} }
@@ -127,6 +131,34 @@
 	return nil
 }
 
+func (m *Mappy) GetS32Booly() map[int32]bool {
+	if m != nil {
+		return m.S32Booly
+	}
+	return nil
+}
+
+func (m *Mappy) GetS64Booly() map[int64]bool {
+	if m != nil {
+		return m.S64Booly
+	}
+	return nil
+}
+
+func (m *Mappy) GetU32Booly() map[uint32]bool {
+	if m != nil {
+		return m.U32Booly
+	}
+	return nil
+}
+
+func (m *Mappy) GetU64Booly() map[uint64]bool {
+	if m != nil {
+		return m.U64Booly
+	}
+	return nil
+}
+
 func init() {
 	proto.RegisterType((*Simple3)(nil), "jsonpb.Simple3")
 	proto.RegisterType((*Mappy)(nil), "jsonpb.Mappy")
@@ -136,28 +168,33 @@
 func init() { proto.RegisterFile("more_test_objects.proto", fileDescriptor0) }
 
 var fileDescriptor0 = []byte{
-	// 357 bytes of a gzipped FileDescriptorProto
-	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x09, 0x6e, 0x88, 0x02, 0xff, 0x84, 0x93, 0xcd, 0x4a, 0xf3, 0x40,
-	0x18, 0x85, 0xbf, 0x34, 0xdf, 0xa4, 0xcd, 0x5b, 0xd0, 0x30, 0x08, 0x0e, 0xba, 0x91, 0x82, 0x50,
-	0x04, 0xb3, 0x68, 0x37, 0xc5, 0x5d, 0x2b, 0x5d, 0x14, 0x69, 0x0a, 0x29, 0xe2, 0xb2, 0x34, 0x3a,
-	0x14, 0x6b, 0xd2, 0x09, 0xf9, 0x11, 0xe6, 0x82, 0xbc, 0x4f, 0xf3, 0x4e, 0x52, 0x33, 0x96, 0x01,
-	0x77, 0xd3, 0x9e, 0xe7, 0x09, 0x67, 0x4e, 0x08, 0x5c, 0x26, 0x22, 0xe3, 0x9b, 0x82, 0xe7, 0xc5,
-	0x46, 0x44, 0x7b, 0xfe, 0x5a, 0xe4, 0x7e, 0x9a, 0x89, 0x42, 0x50, 0x67, 0x9f, 0x8b, 0x43, 0x1a,
-	0x0d, 0xae, 0xa1, 0xbb, 0x7e, 0x4f, 0xd2, 0x98, 0x8f, 0xa9, 0x07, 0xf6, 0x5b, 0x19, 0x31, 0xeb,
-	0xc6, 0x1a, 0x5a, 0x21, 0x1e, 0x07, 0x5f, 0x04, 0xc8, 0x72, 0x9b, 0xa6, 0x92, 0xfa, 0x40, 0x0e,
-	0x65, 0x92, 0xc8, 0x2a, 0xb5, 0x87, 0xfd, 0x11, 0xf3, 0x6b, 0xdd, 0x57, 0xa9, 0x1f, 0x60, 0x34,
-	0x3f, 0x14, 0x99, 0x0c, 0x6b, 0x0c, 0xf9, 0xbc, 0xc8, 0x32, 0xc9, 0x3a, 0x26, 0x7e, 0x8d, 0x51,
-	0xc3, 0x2b, 0x0c, 0xf9, 0xaa, 0xdf, 0x5e, 0x32, 0xdb, 0xc4, 0xaf, 0x30, 0x6a, 0x78, 0x85, 0x21,
-	0x1f, 0x95, 0xbb, 0x9d, 0x64, 0xff, 0x4d, 0xfc, 0x0c, 0xa3, 0x86, 0x57, 0x98, 0xe2, 0x85, 0x88,
-	0x25, 0x23, 0x46, 0x1e, 0xa3, 0x23, 0x8f, 0x67, 0xe4, 0x79, 0x75, 0x13, 0xc9, 0x1c, 0x13, 0x3f,
-	0xc7, 0xa8, 0xe1, 0x15, 0x76, 0x35, 0x01, 0x68, 0x47, 0xc0, 0x25, 0x3f, 0xb8, 0x54, 0x4b, 0xda,
-	0x21, 0x1e, 0xe9, 0x05, 0x90, 0xcf, 0x6d, 0x5c, 0xf2, 0x6a, 0x0f, 0x6b, 0x48, 0xc2, 0xfa, 0xc7,
-	0x43, 0x67, 0x62, 0xa1, 0xd9, 0xce, 0xa1, 0x9b, 0xae, 0xc1, 0x74, 0x75, 0x73, 0x01, 0xd0, 0x0e,
-	0xa3, 0x9b, 0xa4, 0x36, 0x6f, 0x75, 0xb3, 0x3f, 0x3a, 0x3f, 0xde, 0xa1, 0x79, 0xdf, 0x27, 0x25,
-	0xda, 0xcd, 0xfe, 0xaa, 0xef, 0x9e, 0x9a, 0x3f, 0xeb, 0xe9, 0x66, 0xcf, 0x60, 0xf6, 0x4e, 0xea,
-	0xb7, 0x3b, 0x1a, 0x2e, 0xfe, 0xab, 0xfe, 0x59, 0x5b, 0xbf, 0xda, 0x99, 0x67, 0xdb, 0x58, 0x7b,
-	0xd4, 0xdd, 0x3d, 0x74, 0x9b, 0x7f, 0x69, 0x1f, 0xba, 0xcf, 0xc1, 0x53, 0xb0, 0x7a, 0x09, 0xbc,
-	0x7f, 0x14, 0xc0, 0x99, 0x86, 0xd3, 0xd9, 0xe2, 0xd1, 0xb3, 0xa8, 0x0b, 0x24, 0x5c, 0x2d, 0xa7,
-	0x81, 0xd7, 0x89, 0x1c, 0xf5, 0x09, 0x8c, 0xbf, 0x03, 0x00, 0x00, 0xff, 0xff, 0x3d, 0x04, 0xff,
-	0x62, 0x1d, 0x03, 0x00, 0x00,
+	// 442 bytes of a gzipped FileDescriptorProto
+	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x09, 0x6e, 0x88, 0x02, 0xff, 0x8c, 0x94, 0xcf, 0xab, 0xd3, 0x40,
+	0x10, 0xc7, 0x4d, 0xf3, 0xf2, 0x6b, 0xca, 0xd3, 0xb0, 0x08, 0x06, 0xdf, 0x45, 0x1e, 0x08, 0x45,
+	0x30, 0x87, 0x56, 0xf4, 0xa1, 0xa7, 0x56, 0x7a, 0x28, 0xd2, 0x14, 0x52, 0x8a, 0xc7, 0xd2, 0xe8,
+	0x52, 0xac, 0x49, 0x13, 0xf2, 0x43, 0xd8, 0x3f, 0x5e, 0x30, 0xb3, 0xd9, 0x34, 0x9b, 0xb0, 0xa5,
+	0xde, 0x36, 0x7c, 0x3f, 0x9f, 0xce, 0xec, 0xce, 0x50, 0x78, 0x95, 0xa4, 0x39, 0xdd, 0x97, 0xb4,
+	0x28, 0xf7, 0x69, 0x74, 0xa2, 0x3f, 0xca, 0xc2, 0xcf, 0xf2, 0xb4, 0x4c, 0x89, 0x79, 0x2a, 0xd2,
+	0x73, 0x16, 0x3d, 0x3e, 0x80, 0xb5, 0xfd, 0x95, 0x64, 0x31, 0x9d, 0x11, 0x17, 0xf4, 0x9f, 0x55,
+	0xe4, 0x69, 0x6f, 0xb4, 0x89, 0x16, 0xe2, 0xf1, 0xf1, 0xaf, 0x0d, 0xc6, 0xfa, 0x90, 0x65, 0x8c,
+	0xf8, 0x60, 0x9c, 0xab, 0x24, 0x61, 0x75, 0xaa, 0x4f, 0xc6, 0x53, 0xcf, 0x6f, 0x74, 0x9f, 0xa7,
+	0x7e, 0x80, 0xd1, 0xf2, 0x5c, 0xe6, 0x2c, 0x6c, 0x30, 0xe4, 0x8b, 0x32, 0xcf, 0x99, 0x37, 0x52,
+	0xf1, 0x5b, 0x8c, 0x04, 0xcf, 0x31, 0xe4, 0xeb, 0xfe, 0x4e, 0xcc, 0xd3, 0x55, 0xfc, 0x06, 0x23,
+	0xc1, 0x73, 0x0c, 0xf9, 0xa8, 0x3a, 0x1e, 0x99, 0x77, 0xa7, 0xe2, 0x17, 0x18, 0x09, 0x9e, 0x63,
+	0x9c, 0x4f, 0xd3, 0x98, 0x79, 0x86, 0x92, 0xc7, 0xa8, 0xe5, 0xf1, 0x8c, 0x3c, 0xad, 0x6f, 0xc2,
+	0x3c, 0x53, 0xc5, 0x2f, 0x31, 0x12, 0x3c, 0xc7, 0xc8, 0x27, 0xb0, 0x8b, 0xd9, 0xb4, 0x29, 0x61,
+	0x71, 0xe5, 0x61, 0x70, 0x65, 0x91, 0x36, 0xd6, 0x05, 0xe6, 0xe2, 0xc7, 0x0f, 0x8d, 0x68, 0x2b,
+	0x45, 0x91, 0xb6, 0xa2, 0xf8, 0x44, 0xb1, 0x6a, 0x2b, 0x3a, 0x2a, 0x71, 0xd7, 0xaf, 0x58, 0x49,
+	0x15, 0xab, 0xb6, 0x22, 0x28, 0xc5, 0x7e, 0xc5, 0x16, 0x7e, 0xfd, 0x04, 0xd0, 0x0d, 0x1a, 0xb7,
+	0xe5, 0x37, 0x65, 0x7c, 0x5b, 0xf4, 0x10, 0x8f, 0xe4, 0x25, 0x18, 0x7f, 0x0e, 0x71, 0x45, 0xeb,
+	0x99, 0x6b, 0x13, 0x23, 0x6c, 0x3e, 0x3e, 0x8f, 0x9e, 0x34, 0x34, 0xbb, 0x91, 0xcb, 0xa6, 0xa3,
+	0x30, 0x1d, 0xd9, 0x5c, 0x01, 0x74, 0xc3, 0x97, 0x4d, 0xa3, 0x31, 0xdf, 0xca, 0xe6, 0x78, 0xfa,
+	0xa2, 0xbd, 0x89, 0xd8, 0xe9, 0x41, 0x13, 0xdd, 0x5e, 0xdc, 0x6a, 0xdf, 0x19, 0x9a, 0x97, 0x07,
+	0x91, 0x4d, 0x5b, 0x61, 0xda, 0x83, 0xf6, 0xbb, 0x5d, 0x51, 0x5c, 0xbc, 0xd7, 0xfe, 0xf3, 0xae,
+	0xfd, 0xfa, 0x9d, 0x69, 0x7e, 0x88, 0xe5, 0x9f, 0xfa, 0x02, 0xf7, 0xbd, 0x1d, 0x52, 0x3c, 0xc6,
+	0xf5, 0x3e, 0x50, 0x96, 0xa7, 0x7a, 0xeb, 0xfa, 0x43, 0x79, 0x77, 0xad, 0xf2, 0xfd, 0xff, 0xc8,
+	0xd7, 0x2a, 0xdf, 0xdd, 0x90, 0xdf, 0xbd, 0x07, 0x4b, 0xbc, 0x04, 0x19, 0x83, 0xb5, 0x0b, 0xbe,
+	0x05, 0x9b, 0xef, 0x81, 0xfb, 0x8c, 0x00, 0x98, 0xf3, 0x70, 0xbe, 0x58, 0x7d, 0x75, 0x35, 0xe2,
+	0x80, 0x11, 0x6e, 0xd6, 0xf3, 0xc0, 0x1d, 0x45, 0x26, 0xff, 0x6b, 0x9b, 0xfd, 0x0b, 0x00, 0x00,
+	0xff, 0xff, 0xa2, 0x4b, 0xe1, 0x77, 0xf5, 0x04, 0x00, 0x00,
 }
diff --git a/jsonpb/jsonpb_test_proto/more_test_objects.proto b/jsonpb/jsonpb_test_proto/more_test_objects.proto
index 511f021..43b440e 100644
--- a/jsonpb/jsonpb_test_proto/more_test_objects.proto
+++ b/jsonpb/jsonpb_test_proto/more_test_objects.proto
@@ -50,4 +50,8 @@
   map<int64, string> buggy = 4;
   map<bool, bool> booly = 5;
   map<string, Numeral> enumy = 6;
+  map<int32, bool> s32booly = 7;
+  map<int64, bool> s64booly = 8;
+  map<uint32, bool> u32booly = 9;
+  map<uint64, bool> u64booly = 10;
 }