diff --git a/js/modules/types/message.js b/js/modules/types/message.js
index e62f05af6..46843c3a5 100644
--- a/js/modules/types/message.js
+++ b/js/modules/types/message.js
@@ -32,8 +32,7 @@ exports.isValid = () =>
   true;
 
 // Schema
-// Inherits existing schema from attachments:
-exports.inheritSchemaVersion = (message) => {
+exports.initializeSchemaVersion = (message) => {
   const isInitialized = SchemaVersion.isValid(message.schemaVersion) &&
     message.schemaVersion >= 1;
   if (isInitialized) {
@@ -72,7 +71,7 @@ exports.inheritSchemaVersion = (message) => {
 // type UpgradeStep = Message -> Promise Message
 
 // SchemaVersion -> UpgradeStep -> UpgradeStep
-exports.withSchemaVersion = (schemaVersion, upgrade) => {
+exports._withSchemaVersion = (schemaVersion, upgrade) => {
   if (!SchemaVersion.isValid(schemaVersion)) {
     throw new TypeError('`schemaVersion` is invalid');
   }
@@ -82,7 +81,7 @@ exports.withSchemaVersion = (schemaVersion, upgrade) => {
 
   return async (message) => {
     if (!exports.isValid(message)) {
-      console.log('Message.withSchemaVersion: Invalid input message:', message);
+      console.log('Message._withSchemaVersion: Invalid input message:', message);
       return message;
     }
 
@@ -95,7 +94,7 @@ exports.withSchemaVersion = (schemaVersion, upgrade) => {
     const hasExpectedVersion = message.schemaVersion === expectedVersion;
     if (!hasExpectedVersion) {
       console.log(
-        'WARNING: Message.withSchemaVersion: Unexpected version:',
+        'WARNING: Message._withSchemaVersion: Unexpected version:',
         `Expected message to have version ${expectedVersion},`,
         `but got ${message.schemaVersion}.`,
         message
@@ -108,7 +107,7 @@ exports.withSchemaVersion = (schemaVersion, upgrade) => {
       upgradedMessage = await upgrade(message);
     } catch (error) {
       console.log(
-        'Message.withSchemaVersion: error:',
+        'Message._withSchemaVersion: error:',
         // TODO: Use `Errors.toLogFormat`:
         error && error.stack ? error.stack : error
       );
@@ -117,7 +116,7 @@ exports.withSchemaVersion = (schemaVersion, upgrade) => {
 
     if (!exports.isValid(upgradedMessage)) {
       console.log(
-        'Message.withSchemaVersion: Invalid upgraded message:',
+        'Message._withSchemaVersion: Invalid upgraded message:',
         upgradedMessage
       );
       return message;
@@ -133,8 +132,10 @@ exports.withSchemaVersion = (schemaVersion, upgrade) => {
 
 
 // Public API
-//      mapAttachments :: (Attachment -> Promise Attachment) -> Message -> Promise Message
-exports.mapAttachments = upgradeAttachment => async message =>
+//      _mapAttachments :: (Attachment -> Promise Attachment) ->
+//                         Message ->
+//                         Promise Message
+exports._mapAttachments = upgradeAttachment => async message =>
   Object.assign(
     {},
     message,
@@ -143,13 +144,13 @@ exports.mapAttachments = upgradeAttachment => async message =>
     }
   );
 
-const toVersion1 = exports.withSchemaVersion(
+const toVersion1 = exports._withSchemaVersion(
   1,
-  exports.mapAttachments(Attachment.autoOrientJPEG)
+  exports._mapAttachments(Attachment.autoOrientJPEG)
 );
-const toVersion2 = exports.withSchemaVersion(
+const toVersion2 = exports._withSchemaVersion(
   2,
-  exports.mapAttachments(Attachment.replaceUnicodeOrderOverrides)
+  exports._mapAttachments(Attachment.replaceUnicodeOrderOverrides)
 );
 
 // UpgradeStep
diff --git a/test/modules/types/message_test.js b/test/modules/types/message_test.js
index 3f57d70e7..e36538f88 100644
--- a/test/modules/types/message_test.js
+++ b/test/modules/types/message_test.js
@@ -4,7 +4,7 @@ const Message = require('../../../js/modules/types/message');
 
 
 describe('Message', () => {
-  describe('inheritSchemaVersion', () => {
+  describe('initializeSchemaVersion', () => {
     it('should ignore messages with previously inherited schema', () => {
       const input = {
         body: 'Imagine there is no heaven…',
@@ -15,7 +15,7 @@ describe('Message', () => {
         schemaVersion: 2,
       };
 
-      const actual = Message.inheritSchemaVersion(input);
+      const actual = Message.initializeSchemaVersion(input);
       assert.deepEqual(actual, expected);
     });
 
@@ -31,7 +31,7 @@ describe('Message', () => {
           schemaVersion: 0,
         };
 
-        const actual = Message.inheritSchemaVersion(input);
+        const actual = Message.initializeSchemaVersion(input);
         assert.deepEqual(actual, expected);
       });
     });
@@ -55,7 +55,7 @@ describe('Message', () => {
           schemaVersion: 7,
         };
 
-        const actual = Message.inheritSchemaVersion(input);
+        const actual = Message.initializeSchemaVersion(input);
         assert.deepEqual(actual, expected);
       });
     });
@@ -116,9 +116,9 @@ describe('Message', () => {
         const v3 = async message =>
           Object.assign({}, message, { hasUpgradedToVersion3: true });
 
-        const toVersion1 = Message.withSchemaVersion(1, v1);
-        const toVersion2 = Message.withSchemaVersion(2, v2);
-        const toVersion3 = Message.withSchemaVersion(3, v3);
+        const toVersion1 = Message._withSchemaVersion(1, v1);
+        const toVersion2 = Message._withSchemaVersion(2, v2);
+        const toVersion3 = Message._withSchemaVersion(3, v3);
 
         const upgradeSchema = async message =>
           toVersion3(await toVersion2(await toVersion1(message)));
@@ -156,9 +156,9 @@ describe('Message', () => {
         const v3 = async attachment =>
           Object.assign({}, attachment, { hasUpgradedToVersion3: true });
 
-        const toVersion1 = Message.withSchemaVersion(1, v1);
-        const toVersion2 = Message.withSchemaVersion(2, v2);
-        const toVersion3 = Message.withSchemaVersion(3, v3);
+        const toVersion1 = Message._withSchemaVersion(1, v1);
+        const toVersion2 = Message._withSchemaVersion(2, v2);
+        const toVersion3 = Message._withSchemaVersion(3, v3);
 
         // NOTE: We upgrade to 3 before 2, i.e. the pipeline should abort:
         const upgradeSchema = async attachment =>
@@ -170,18 +170,18 @@ describe('Message', () => {
     });
   });
 
-  describe('withSchemaVersion', () => {
+  describe('_withSchemaVersion', () => {
     it('should require a version number', () => {
       const toVersionX = () => {};
       assert.throws(
-        () => Message.withSchemaVersion(toVersionX, 2),
+        () => Message._withSchemaVersion(toVersionX, 2),
         '`schemaVersion` is invalid'
       );
     });
 
     it('should require an upgrade function', () => {
       assert.throws(
-        () => Message.withSchemaVersion(2, 3),
+        () => Message._withSchemaVersion(2, 3),
         '`upgrade` must be a function'
       );
     });
@@ -189,7 +189,7 @@ describe('Message', () => {
     it('should skip upgrading if message has already been upgraded', async () => {
       const upgrade = async message =>
         Object.assign({}, message, { foo: true });
-      const upgradeWithVersion = Message.withSchemaVersion(3, upgrade);
+      const upgradeWithVersion = Message._withSchemaVersion(3, upgrade);
 
       const input = {
         id: 'guid-guid-guid-guid',
@@ -207,7 +207,7 @@ describe('Message', () => {
       const upgrade = async () => {
         throw new Error('boom!');
       };
-      const upgradeWithVersion = Message.withSchemaVersion(3, upgrade);
+      const upgradeWithVersion = Message._withSchemaVersion(3, upgrade);
 
       const input = {
         id: 'guid-guid-guid-guid',
@@ -223,7 +223,7 @@ describe('Message', () => {
 
     it('should return original message if upgrade function returns null', async () => {
       const upgrade = async () => null;
-      const upgradeWithVersion = Message.withSchemaVersion(3, upgrade);
+      const upgradeWithVersion = Message._withSchemaVersion(3, upgrade);
 
       const input = {
         id: 'guid-guid-guid-guid',