diff --git a/web/base_viewer.js b/web/base_viewer.js
index e084512b0..2eee52ac9 100644
--- a/web/base_viewer.js
+++ b/web/base_viewer.js
@@ -1035,9 +1035,18 @@ class BaseViewer {
   }
 
   _updateScrollModeClasses() {
-    const mode = this.scrollMode, { classList, } = this.viewer;
-    classList.toggle('scrollHorizontal', mode === ScrollMode.HORIZONTAL);
-    classList.toggle('scrollWrapped', mode === ScrollMode.WRAPPED);
+    const { scrollMode, viewer, } = this;
+
+    if (scrollMode === ScrollMode.HORIZONTAL) {
+      viewer.classList.add('scrollHorizontal');
+    } else {
+      viewer.classList.remove('scrollHorizontal');
+    }
+    if (scrollMode === ScrollMode.WRAPPED) {
+      viewer.classList.add('scrollWrapped');
+    } else {
+      viewer.classList.remove('scrollWrapped');
+    }
   }
 
   setSpreadMode(mode) {
diff --git a/web/secondary_toolbar.js b/web/secondary_toolbar.js
index a44be0642..233f5f6fa 100644
--- a/web/secondary_toolbar.js
+++ b/web/secondary_toolbar.js
@@ -190,23 +190,41 @@ class SecondaryToolbar {
 
   _bindScrollModeListener(buttons) {
     this.eventBus.on('scrollmodechanged', function(evt) {
-      buttons.scrollVerticalButton.classList.toggle('toggled',
-        evt.mode === ScrollMode.VERTICAL);
-      buttons.scrollHorizontalButton.classList.toggle('toggled',
-        evt.mode === ScrollMode.HORIZONTAL);
-      buttons.scrollWrappedButton.classList.toggle('toggled',
-        evt.mode === ScrollMode.WRAPPED);
+      buttons.scrollVerticalButton.classList.remove('toggled');
+      buttons.scrollHorizontalButton.classList.remove('toggled');
+      buttons.scrollWrappedButton.classList.remove('toggled');
+
+      switch (evt.mode) {
+        case ScrollMode.VERTICAL:
+          buttons.scrollVerticalButton.classList.add('toggled');
+          break;
+        case ScrollMode.HORIZONTAL:
+          buttons.scrollHorizontalButton.classList.add('toggled');
+          break;
+        case ScrollMode.WRAPPED:
+          buttons.scrollWrappedButton.classList.add('toggled');
+          break;
+      }
     });
   }
 
   _bindSpreadModeListener(buttons) {
     this.eventBus.on('spreadmodechanged', function(evt) {
-      buttons.spreadNoneButton.classList.toggle('toggled',
-        evt.mode === SpreadMode.NONE);
-      buttons.spreadOddButton.classList.toggle('toggled',
-        evt.mode === SpreadMode.ODD);
-      buttons.spreadEvenButton.classList.toggle('toggled',
-        evt.mode === SpreadMode.EVEN);
+      buttons.spreadNoneButton.classList.remove('toggled');
+      buttons.spreadOddButton.classList.remove('toggled');
+      buttons.spreadEvenButton.classList.remove('toggled');
+
+      switch (evt.mode) {
+        case SpreadMode.NONE:
+          buttons.spreadNoneButton.classList.add('toggled');
+          break;
+        case SpreadMode.ODD:
+          buttons.spreadOddButton.classList.add('toggled');
+          break;
+        case SpreadMode.EVEN:
+          buttons.spreadEvenButton.classList.add('toggled');
+          break;
+      }
     });
   }