diff --git a/src/structs/ContentFormat.js b/src/structs/ContentFormat.js
index 4b82bba7..6ac4c29c 100644
--- a/src/structs/ContentFormat.js
+++ b/src/structs/ContentFormat.js
@@ -100,4 +100,4 @@ export class ContentFormat {
  * @param {UpdateDecoderV1 | UpdateDecoderV2} decoder
  * @return {ContentFormat}
  */
-export const readContentFormat = decoder => new ContentFormat(decoder.readString(), decoder.readJSON())
+export const readContentFormat = decoder => new ContentFormat(decoder.readKey(), decoder.readJSON())
diff --git a/src/utils/UpdateEncoder.js b/src/utils/UpdateEncoder.js
index a7c301d3..e8c5d06c 100644
--- a/src/utils/UpdateEncoder.js
+++ b/src/utils/UpdateEncoder.js
@@ -298,10 +298,24 @@ export class UpdateEncoderV2 extends DSEncoderV2 {
   writeKey (key) {
     const clock = this.keyMap.get(key)
     if (clock === undefined) {
+      /**
+       * @todo uncomment to introduce this feature finally
+       *
+       * Background. The ContentFormat object was always encoded using writeKey, but the decoder used to use readString.
+       * Furthermore, I forgot to set the keyclock. So everything was working fine.
+       *
+       * However, this feature here is basically useless as it is not being used (it actually only consumes extra memory).
+       *
+       * I don't know yet how to reintroduce this feature..
+       *
+       * Older clients won't be able to read updates when we reintroduce this feature. So this should probably be done using a flag.
+       *
+       */
+      // this.keyMap.set(key, this.keyClock)
       this.keyClockEncoder.write(this.keyClock++)
       this.stringEncoder.write(key)
     } else {
-      this.keyClockEncoder.write(this.keyClock++)
+      this.keyClockEncoder.write(clock)
     }
   }
 }
diff --git a/tests/updates.tests.js b/tests/updates.tests.js
index 9ae50440..dce09e71 100644
--- a/tests/updates.tests.js
+++ b/tests/updates.tests.js
@@ -112,6 +112,24 @@ export const testMergeUpdates = tc => {
   })
 }
 
+/**
+ * @param {t.TestCase} tc
+ */
+export const testKeyEncoding = tc => {
+  const { users, text0, text1 } = init(tc, { users: 2 })
+
+  text0.insert(0, 'a', { italic: true })
+  text0.insert(0, 'b')
+  text0.insert(0, 'c', { italic: true })
+
+  const update = Y.encodeStateAsUpdateV2(users[0])
+  Y.applyUpdateV2(users[1], update)
+
+  t.compare(text1.toDelta(), [{ insert: 'c', attributes: { italic: true } }, { insert: 'b' }, { insert: 'a', attributes: { italic: true } }])
+
+  compare(users)
+}
+
 /**
  * @param {Y.Doc} ydoc
  * @param {Array<Uint8Array>} updates - expecting at least 4 updates