diff --git a/src/resizer/distributors.js b/src/resizer/distributors.js
index 3c3fd72621..caf677a18f 100644
--- a/src/resizer/distributors.js
+++ b/src/resizer/distributors.js
@@ -18,43 +18,46 @@ limitations under the License.
 distributors translate a moving cursor into
 CSS/DOM changes by calling the sizer
 
-they have one method, `resize` that receives
+they have two methods:
+    `resize` receives then new item size
+    `resizeFromContainerOffset` receives resize handle location
+        within the container bounding box. For internal use.
+        This method usually ends up calling `resize` once the start offset is subtracted.
 the offset from the container edge of where
 the mouse cursor is.
 */
 class FixedDistributor {
-    constructor(sizer, item, config) {
+    constructor(sizer, item, id, config) {
         this.sizer = sizer;
         this.item = item;
+        this.id = id;
         this.beforeOffset = sizer.getItemOffset(this.item);
         this.onResized = config && config.onResized;
     }
 
-    resize(offset) {
-        const itemSize = offset - this.beforeOffset;
+    resize(itemSize) {
         this.sizer.setItemSize(this.item, itemSize);
         if (this.onResized) {
-            this.onResized(itemSize, this.item);
+            this.onResized(itemSize, this.id, this.item);
         }
         return itemSize;
     }
 
-    sizeFromOffset(offset) {
-        return offset - this.beforeOffset;
+    resizeFromContainerOffset(offset) {
+        this.resize(offset - this.beforeOffset);
     }
 }
 
 
 class CollapseDistributor extends FixedDistributor {
-    constructor(sizer, item, config) {
-        super(sizer, item, config);
+    constructor(sizer, item, id, config) {
+        super(sizer, item, id, config);
         this.toggleSize = config && config.toggleSize;
         this.onCollapsed = config && config.onCollapsed;
         this.isCollapsed = false;
     }
 
-    resize(offset) {
-        const newSize = this.sizeFromOffset(offset);
+    resize(newSize) {
         const isCollapsedSize = newSize < this.toggleSize;
         if (isCollapsedSize && !this.isCollapsed) {
             this.isCollapsed = true;
@@ -68,7 +71,7 @@ class CollapseDistributor extends FixedDistributor {
             this.isCollapsed = false;
         }
         if (!isCollapsedSize) {
-            super.resize(offset);
+            super.resize(newSize);
         }
     }
 }
diff --git a/src/resizer/resizer.js b/src/resizer/resizer.js
index c5112e5139..b7d17bc807 100644
--- a/src/resizer/resizer.js
+++ b/src/resizer/resizer.js
@@ -88,7 +88,7 @@ export class Resizer {
 
         const onMouseMove = (event) => {
             const offset = sizer.offsetFromEvent(event);
-            distributor.resize(offset);
+            distributor.resizeFromContainerOffset(offset);
         };
 
         const body = document.body;
diff --git a/src/resizer/room.js b/src/resizer/room.js
index 2b79c4adf8..70f8be219a 100644
--- a/src/resizer/room.js
+++ b/src/resizer/room.js
@@ -36,16 +36,19 @@ class RoomSizer extends Sizer {
 }
 
 class RoomDistributor extends FixedDistributor {
-    resize(offset) {
-        const itemSize = offset - this.sizer.getItemOffset(this.item);
+    resize(itemSize) {
         const scrollItem = this.item.querySelector(".mx_RoomSubList_scroll");
         const fixedHeight = this.item.offsetHeight - scrollItem.offsetHeight;
         if (itemSize > (fixedHeight + scrollItem.scrollHeight)) {
-            this.sizer.setItemSize(this.item, "resized-all");
+            super.resize("resized-all");
         } else {
-            this.sizer.setItemSize(this.item, itemSize);
+            super.resize(itemSize);
         }
     }
+
+    resizeFromContainerOffset(offset) {
+        return this.resize(offset - this.sizer.getItemOffset(this.item));
+    }
 }
 
 module.exports = {