--- a/browser/themes/shared/tabs.css
+++ b/browser/themes/shared/tabs.css
@@ -93,16 +93,20 @@
   border-width: 0;
   margin: 0;
   padding: 0 2px;
   -moz-box-align: stretch;
   /* Needed so that overflowing content overflows towards the end rather than
      getting centered. That prevents tab opening animation from looking off at
      the start, see bug 1759221. */
   -moz-box-pack: start;
+  overflow: clip;
+  /* Needed to avoid clipping the tab-background shadow, which has a 4px blur
+   * (we only have 2px padding in the inline direction) */
+  overflow-clip-margin: 2px;
   min-height: var(--tab-min-height);
 }
 
 /* tabbrowser-tab keyboard focus */
 .keyboard-focused-tab > .tab-stack > .tab-background,
 .tabbrowser-tab:focus:not([aria-activedescendant]) > .tab-stack > .tab-background {
   outline: var(--focus-outline);
   outline-offset: var(--focus-outline-inset);