diff --git a/polygerrit-ui/app/BUILD b/polygerrit-ui/app/BUILD
index d0e9b91..329b195 100644
--- a/polygerrit-ui/app/BUILD
+++ b/polygerrit-ui/app/BUILD
@@ -133,7 +133,6 @@
     "elements/change/gr-thread-list/gr-thread-list_html.ts",
     "elements/diff/gr-diff-builder/gr-diff-builder-element_html.ts",
     "elements/diff/gr-diff-host/gr-diff-host_html.ts",
-    "elements/diff/gr-diff-mode-selector/gr-diff-mode-selector_html.ts",
     "elements/diff/gr-diff-preferences-dialog/gr-diff-preferences-dialog_html.ts",
     "elements/diff/gr-diff-view/gr-diff-view_html.ts",
     "elements/diff/gr-diff/gr-diff_html.ts",
diff --git a/polygerrit-ui/app/elements/diff/gr-diff-mode-selector/gr-diff-mode-selector.ts b/polygerrit-ui/app/elements/diff/gr-diff-mode-selector/gr-diff-mode-selector.ts
index 0f8752d..6fe9d27 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-mode-selector/gr-diff-mode-selector.ts
+++ b/polygerrit-ui/app/elements/diff/gr-diff-mode-selector/gr-diff-mode-selector.ts
@@ -73,19 +73,19 @@
     }
   }
 
-  _computeSideBySideSelected(mode: DiffViewMode) {
+  _computeSideBySideSelected(mode?: DiffViewMode) {
     return mode === DiffViewMode.SIDE_BY_SIDE ? 'selected' : '';
   }
 
-  _computeUnifiedSelected(mode: DiffViewMode) {
+  _computeUnifiedSelected(mode?: DiffViewMode) {
     return mode === DiffViewMode.UNIFIED ? 'selected' : '';
   }
 
-  isSideBySideSelected(mode: DiffViewMode) {
+  isSideBySideSelected(mode?: DiffViewMode) {
     return mode === DiffViewMode.SIDE_BY_SIDE;
   }
 
-  isUnifiedSelected(mode: DiffViewMode) {
+  isUnifiedSelected(mode?: DiffViewMode) {
     return mode === DiffViewMode.UNIFIED;
   }
 
diff --git a/polygerrit-ui/app/elements/diff/gr-diff-mode-selector/gr-diff-mode-selector_html.ts b/polygerrit-ui/app/elements/diff/gr-diff-mode-selector/gr-diff-mode-selector_html.ts
index 3ebb58f..4e2b6a1 100644
--- a/polygerrit-ui/app/elements/diff/gr-diff-mode-selector/gr-diff-mode-selector_html.ts
+++ b/polygerrit-ui/app/elements/diff/gr-diff-mode-selector/gr-diff-mode-selector_html.ts
@@ -37,7 +37,7 @@
     position-below="[[showTooltipBelow]]"
     class$="[[_computeSideBySideSelected(mode)]]"
     title="Side-by-side diff"
-    aria-pressed="[[isSideBySideSelected(mode)]]"
+    aria-pressed$="[[isSideBySideSelected(mode)]]"
     on-click="_handleSideBySideTap"
   >
     <iron-icon icon="gr-icons:side-by-side"></iron-icon>
@@ -49,7 +49,7 @@
     position-below="[[showTooltipBelow]]"
     title="Unified diff"
     class$="[[_computeUnifiedSelected(mode)]]"
-    aria-pressed="[[isUnifiedSelected(mode)]]"
+    aria-pressed$="[[isUnifiedSelected(mode)]]"
     on-click="_handleUnifiedTap"
   >
     <iron-icon icon="gr-icons:unified"></iron-icon>