diff --git a/README.markdown b/README.markdown
index 43c5dce74..c4813e384 100644
--- a/README.markdown
+++ b/README.markdown
@@ -339,7 +339,15 @@ Generated code will be placed in the Gradle build directory.
 
 - With `--ts_proto_opt=lowerCaseServiceMethods=true`, the method names of service methods will be lowered/camel-case, i.e. `service.findFoo` instead of `service.FindFoo`.
 
-- With `--ts_proto_opt=snakeToCamel=false`, fields will be kept snake case. `snakeToCamel` can also be set as string with `--ts_proto_opt=snakeToCamel=keys,json`. `keys` will keep field names as camelCase and `json` will keep json field names as camelCase. Empty string will keep field names as snake_case.
+- With `--ts_proto_opt=snakeToCamel=false`, fields will be kept snake case in both the message keys and the `toJSON` / `fromJSON` methods.
+
+  `snakeToCamel` can also be set as a `_`-delimited list of strings (comma is reserved as the flag delimited), i.e. `--ts_proto_opt=snakeToCamel=keys_json`, where including `keys` will make message keys be camel case and including `json` will make JSON keys be camel case.
+
+   Empty string, i.e. `snakeToCamel=`, will keep both messages keys and `JSON` keys as snake case (it is the same as `snakeToCamel=false`).
+
+   Note that to use the `json_name` attribute, you'll have to use the `json`.
+
+   The default behavior is `keys_json`, i.e. both will be camel cased, and `json_name` will be used if set.
 
 - With `--ts_proto_opt=outputEncodeMethods=false`, the `Message.encode` and `Message.decode` methods for working with protobuf-encoded/binary data will not be output.
 
diff --git a/src/options.ts b/src/options.ts
index f19acab94..549ef4f50 100644
--- a/src/options.ts
+++ b/src/options.ts
@@ -176,7 +176,7 @@ export function optionsFromParameter(parameter: string | undefined): Options {
   } else if ((options.snakeToCamel as any) === true) {
     options.snakeToCamel = ['keys', 'json'];
   } else if (typeof options.snakeToCamel === 'string') {
-    options.snakeToCamel = [options.snakeToCamel];
+    options.snakeToCamel = (options.snakeToCamel as string).split('_') as any;
   }
 
   if (options.useJsonWireFormat) {
diff --git a/tests/options-test.ts b/tests/options-test.ts
index efb733c61..ccbbc6b55 100644
--- a/tests/options-test.ts
+++ b/tests/options-test.ts
@@ -98,6 +98,11 @@ describe('options', () => {
     expect(options).toMatchObject({ snakeToCamel: ['keys'] });
   });
 
+  it('can set snakeToCamel as two values', () => {
+    const options = optionsFromParameter('snakeToCamel=keys_json');
+    expect(options).toMatchObject({ snakeToCamel: ['keys', 'json'] });
+  });
+
   it('can set multiple values as an array', () => {
     const options = optionsFromParameter('foo=one,foo=two');
     expect(options).toMatchObject({ foo: ['one', 'two'] });