diff --git a/google/protobuf/descriptor.proto b/google/protobuf/descriptor.proto
index 8f90a956cf92f..801d85e44624f 100644
--- a/google/protobuf/descriptor.proto
+++ b/google/protobuf/descriptor.proto
@@ -191,6 +191,12 @@ message FieldDescriptorProto {
   // list.  This field is a member of that oneof.
   optional int32 oneof_index = 9;
 
+  // JSON name of this field. The value is set by protocol compiler. If the
+  // user has set a "json_name" option on this field, that option's value
+  // will be used. Otherwise, it's deduced from the field's name by converting
+  // it to camelCase.
+  optional string json_name = 10;
+
   optional FieldOptions options = 8;
 }
 
diff --git a/google/protobuf/map_proto2_unittest.proto b/google/protobuf/map_proto2_unittest.proto
index 6f9d6165c6fbe..916cc54637538 100644
--- a/google/protobuf/map_proto2_unittest.proto
+++ b/google/protobuf/map_proto2_unittest.proto
@@ -31,6 +31,8 @@
 syntax = "proto2";
 
 
+import "google/protobuf/unittest_import.proto";
+
 // We don't put this in a package within proto2 because we need to make sure
 // that the generated code doesn't depend on being in the proto2 namespace.
 // In map_test_util.h we do "using namespace unittest = protobuf_unittest".
@@ -58,3 +60,7 @@ message TestEnumMapPlusExtra {
   map<int32, Proto2MapEnumPlusExtra> known_map_field = 101;
   map<int32, Proto2MapEnumPlusExtra> unknown_map_field = 102;
 }
+
+message TestImportEnumMap {
+  map<int32, protobuf_unittest_import.ImportEnumForMap> import_enum_amp = 1;
+}
diff --git a/google/protobuf/unittest_import.proto b/google/protobuf/unittest_import.proto
index 7e165220334f5..8d03e3888bc92 100644
--- a/google/protobuf/unittest_import.proto
+++ b/google/protobuf/unittest_import.proto
@@ -64,3 +64,10 @@ enum ImportEnum {
   IMPORT_BAZ = 9;
 }
 
+
+// To use an enum in a map, it must has the first value as 0.
+enum ImportEnumForMap {
+  UNKNOWN = 0;
+  FOO = 1;
+  BAR = 2;
+}
diff --git a/google/protobuf/util/json_format_proto3.proto b/google/protobuf/util/json_format_proto3.proto
index 7a2828681e065..e81376778c177 100644
--- a/google/protobuf/util/json_format_proto3.proto
+++ b/google/protobuf/util/json_format_proto3.proto
@@ -100,6 +100,16 @@ message TestMap {
   map<string, int32> string_map = 6;
 }
 
+message TestNestedMap {
+  map<bool, int32> bool_map = 1;
+  map<int32, int32> int32_map = 2;
+  map<int64, int32> int64_map = 3;
+  map<uint32, int32> uint32_map = 4;
+  map<uint64, int32> uint64_map = 5;
+  map<string, int32> string_map = 6;
+  map<string, TestNestedMap> map_map = 7;
+}
+
 message TestWrapper {
   google.protobuf.BoolValue bool_value = 1;
   google.protobuf.Int32Value int32_value = 2;