--- a/browser/themes/linux/browser.css
+++ b/browser/themes/linux/browser.css
@@ -732,18 +732,16 @@ html|span.ac-emphasize-text-url {
 }
 
 #UITourTooltipDescription {
   font-size: 1.05rem;
 }
 
 #UITourTooltipClose {
   margin-inline-end: -4px;
-  height: 16px;
-  width: 16px;
 }
 
 /**
  * Override the --arrowpanel-padding so the background extends
  * to the sides and bottom of the panel.
  */
 #UITourTooltipButtons {
   margin-left: -10px;

--- a/browser/themes/osx/browser.css
+++ b/browser/themes/osx/browser.css
@@ -1266,22 +1266,16 @@ html|*.addon-webext-perm-list {
   line-height: 2rem;
 }
 
 #UITourTooltipClose {
   margin-inline-end: -10px;
   margin-top: -14px;
 }
 
-@media (min-resolution: 2dppx) {
-  #UITourTooltipClose > .toolbarbutton-icon {
-    width: 16px;
-  }
-}
-
 %include ../shared/contextmenu.inc.css
 
 #context-navigation > .menuitem-iconic {
   padding-left: 0;
   padding-right: 0;
 }
 
 .browser-extension-panel > .panel-arrowcontainer > .panel-arrowcontent {