diff --git a/res/css/views/rooms/_RoomSublist2.scss b/res/css/views/rooms/_RoomSublist2.scss
index 0e76152f86..e080f0efb4 100644
--- a/res/css/views/rooms/_RoomSublist2.scss
+++ b/res/css/views/rooms/_RoomSublist2.scss
@@ -70,6 +70,7 @@ limitations under the License.
                 z-index: 1; // over top of other elements, but still under the ones in the visible list
                 height: 32px; // to match the header container
                 // width set by JS
+                width: calc(100% - 22px);
             }
 
             &.mx_RoomSublist2_headerContainer_stickyBottom {
diff --git a/src/components/structures/LeftPanel2.tsx b/src/components/structures/LeftPanel2.tsx
index 88446e02f5..ccd4049c88 100644
--- a/src/components/structures/LeftPanel2.tsx
+++ b/src/components/structures/LeftPanel2.tsx
@@ -124,13 +124,11 @@ export default class LeftPanel2 extends React.Component<IProps, IState> {
             if (slRect.top + headerHeight > bottom && !gotBottom) {
                 header.classList.add("mx_RoomSublist2_headerContainer_sticky");
                 header.classList.add("mx_RoomSublist2_headerContainer_stickyBottom");
-                header.style.width = `${headerStickyWidth}px`;
                 header.style.top = `unset`;
                 gotBottom = true;
             } else if (slRect.top < top) {
                 header.classList.add("mx_RoomSublist2_headerContainer_sticky");
                 header.classList.add("mx_RoomSublist2_headerContainer_stickyTop");
-                header.style.width = `${headerStickyWidth}px`;
                 header.style.top = `${rlRect.top}px`;
                 if (lastTopHeader) {
                     lastTopHeader.style.display = "none";
@@ -142,7 +140,6 @@ export default class LeftPanel2 extends React.Component<IProps, IState> {
                 header.classList.remove("mx_RoomSublist2_headerContainer_sticky");
                 header.classList.remove("mx_RoomSublist2_headerContainer_stickyTop");
                 header.classList.remove("mx_RoomSublist2_headerContainer_stickyBottom");
-                header.style.width = `unset`;
                 header.style.top = `unset`;
             }
         }