diff --git a/src/types/YText.js b/src/types/YText.js
index 053f23a2..f9d36394 100644
--- a/src/types/YText.js
+++ b/src/types/YText.js
@@ -1016,11 +1016,12 @@ export class YText extends AbstractType {
         let attributions = null
         if (attrs != null) {
           attributions = {}
+          attributions.changeType = deleted ? 'delete' : 'insert'
           attrs.forEach(attr => {
             switch (attr.name) {
-              case '_insertedBy':
-              case '_deletedBy':
-              case '_suggestedBy': {
+              case 'insertedBy':
+              case 'deletedBy':
+              case 'suggestedBy': {
                 const as = /** @type {any} */ (attributions)
                 const ls = as[attr.name] = as[attr.name] ?? []
                 ls.push(attr.val)
@@ -1046,10 +1047,15 @@ export class YText extends AbstractType {
           }
           case ContentFormat:
             if (attributions != null) {
-              attributions.formattedBy = (deleted ? attributions.deletedBy : attributions.insertedBy) ?? []
-              delete attributions.deletedBy
-              delete attributions.insertedBy
-              d.useAttribution(attributions)
+              if (deleted) {
+                d.useAttribution(null)
+              } else {
+                attributions.formattedBy = (deleted ? attributions.deletedBy : attributions.insertedBy) ?? []
+                attributions.changeType = 'format'
+                delete attributions.deletedBy
+                delete attributions.insertedBy
+                d.useAttribution(attributions)
+              }
             }
             break
         }
diff --git a/src/utils/Delta.js b/src/utils/Delta.js
index 60f12c4b..c1c5b525 100644
--- a/src/utils/Delta.js
+++ b/src/utils/Delta.js
@@ -106,22 +106,22 @@ export class DeltaBuilder extends Delta {
   }
 
   /**
-   * @param {FormattingAttributes} attributes
+   * @param {FormattingAttributes?} attributes
    * @return {this}
    */
   useAttributes (attributes) {
     if (this._useAttributes === attributes) return this
-    this._useAttributes = object.assign({}, attributes)
+    this._useAttributes = attributes && object.assign({}, attributes)
     if (this._lastOp?.constructor !== DeleteOp) this._lastOp = null
     return this
   }
 
   /**
-   * @param {Attribution} attribution
+   * @param {Attribution?} attribution
    */
   useAttribution (attribution) {
     if (this._useAttribution === attribution) return this
-    this._useAttribution = object.assign({}, attribution)
+    this._useAttribution = attribution && object.assign({}, attribution)
     if (this._lastOp?.constructor !== DeleteOp) this._lastOp = null
     return this
   }
diff --git a/src/utils/IdMap.js b/src/utils/IdMap.js
index 0e0d3197..522fb81a 100644
--- a/src/utils/IdMap.js
+++ b/src/utils/IdMap.js
@@ -110,6 +110,16 @@ export class AttrRange {
  * @typedef {{ clock: number, len: number, attrs: Array<Attribution<Attrs>>? }} MaybeAttrRange
  */
 
+/**
+ * @template Attrs
+ *
+ * @param {number} clock
+ * @param {number} len
+ * @param {Array<Attribution<Attrs>>?} attrs
+ * @return {MaybeAttrRange<Attrs>}
+ */
+export const createMaybeAttrRange = (clock, len, attrs) => new AttrRange(clock, len, /** @type {any} */ (attrs))
+
 /**
  * @template Attrs
  */
@@ -238,21 +248,18 @@ export const mergeIdMaps = ams => {
       if (!merged.clients.has(client)) {
         // Write all missing keys from current set and all following.
         // If merged already contains `client` current ds has already been added.
-        const ids = rangesLeft.getIds().slice()
+        let ids = rangesLeft.getIds().slice()
         for (let i = amsI + 1; i < ams.length; i++) {
           const nextIds = ams[i].clients.get(client)
           if (nextIds) {
             array.appendTo(ids, nextIds.getIds())
           }
         }
-        ids.forEach(id => {
-          // @ts-ignore
-          id.attrs = id.attrs.map(attr =>
-            map.setIfUndefined(attrMapper, attr, () =>
-              _ensureAttrs(merged, [attr])[0]
-            )
+        ids = ids.map(id => new AttrRange(id.clock, id.len, id.attrs.map(attr =>
+          map.setIfUndefined(attrMapper, attr, () =>
+            _ensureAttrs(merged, [attr])[0]
           )
-        })
+        )))
         merged.clients.set(client, new AttrRanges(ids))
       }
     })
@@ -323,7 +330,7 @@ export class IdMap {
           if (r.len <= 0) break
           const prevEnd = prev != null ? prev.clock + prev.len : index
           if (prevEnd < index) {
-            res.push(/** @type {MaybeAttrRange<Attrs>} */ (new AttrRange(prevEnd, index - prevEnd, /** @type {any} */ (null))))
+            res.push(createMaybeAttrRange(prevEnd, index - prevEnd, null))
           }
           prev = r
           res.push(r)
@@ -335,10 +342,10 @@ export class IdMap {
       const last = res[res.length - 1]
       const end = last.clock + last.len
       if (end < id.clock + len) {
-        res.push(new AttrRange(end, id.clock + len - end, []))
+        res.push(createMaybeAttrRange(end, id.clock + len - end, null))
       }
     } else {
-      res.push(new AttrRange(id.clock, len, []))
+      res.push(createMaybeAttrRange(id.clock, len, null))
     }
     return res
   }
diff --git a/tests/IdMap.tests.js b/tests/IdMap.tests.js
index 68a595ca..79809e2e 100644
--- a/tests/IdMap.tests.js
+++ b/tests/IdMap.tests.js
@@ -1,6 +1,6 @@
 import * as t from 'lib0/testing'
 import * as idmap from '../src/utils/IdMap.js'
-import { compareIdmaps, createIdMap, ID, createRandomIdSet, createRandomIdMap, createAttribution } from './testHelper.js'
+import { compareIdmaps, createIdMap, ID, createRandomIdSet, createRandomIdMap, createAttribution, validateIdMap } from './testHelper.js'
 import * as YY from '../src/internals.js'
 
 /**
@@ -93,13 +93,11 @@ export const testRepeatMergingMultipleIdMaps = tc => {
       const oneHas = sets.some(ids => ids.has(new ID(iclient, iclock)))
       t.assert(mergedHas === oneHas)
       const mergedAttrs = merged.slice(new ID(iclient, iclock), 1)
-      if (mergedAttrs) {
-        mergedAttrs.forEach(a => {
-          if (a.attrs != null) {
-            composed.add(iclient, a.clock, a.len, a.attrs)
-          }
-        })
-      }
+      mergedAttrs.forEach(a => {
+        if (a.attrs != null) {
+          composed.add(iclient, a.clock, a.len, a.attrs)
+        }
+      })
     }
   }
   compareIdmaps(merged, composed)