--- a/devtools/client/themes/animationinspector.css
+++ b/devtools/client/themes/animationinspector.css
@@ -241,17 +241,18 @@ body {
   overflow: hidden;
 }
 
 /* Animation timeline component */
 
 .animation-timeline {
   position: relative;
   width: 100%;
-  overflow: auto;
+  overflow-y: auto;
+  overflow-x: hidden;
 }
 
 /* Useful for positioning animations or keyframes in the timeline */
 .animation-detail .track-container,
 .animation-timeline .track-container {
   position: absolute;
   top: 0;
   left: var(--timeline-sidebar-width);