--- a/browser/themes/linux/syncedtabs/sidebar.css
+++ b/browser/themes/linux/syncedtabs/sidebar.css
@@ -41,21 +41,23 @@ html {
 .textbox-search-clear {
   background-image: url(moz-icon://stock/gtk-clear?size=menu);
   background-repeat: no-repeat;
   width: 16px;
   height: 16px;
 }
 
 .textbox-search-icon {
+  width: 16px;
+  height: 16px;
   background-image: url(chrome://global/skin/icons/search-textbox.svg);
   background-repeat: no-repeat;
-  width: 16px;
-  height: 16px;
-  display: block;
+  background-position: center;
+  display: inline-block;
+  vertical-align: middle;
 }
 
 .textbox-search-icon[searchbutton]:not([disabled]) ,
 .textbox-search-clear:not([disabled]) {
   cursor: pointer;
 }
 
 .item.client .item-twisty-container {

--- a/browser/themes/windows/syncedtabs/sidebar.css
+++ b/browser/themes/windows/syncedtabs/sidebar.css
@@ -31,17 +31,19 @@ html {
   color: -moz-FieldText;
 }
 
 .textbox-search-icon {
   width: 16px;
   height: 16px;
   background-image: url(chrome://global/skin/icons/search-textbox.svg);
   background-repeat: no-repeat;
-  display: block;
+  background-position: center;
+  display: inline-block;
+  vertical-align: middle;
 }
 
 .textbox-search-icon:-moz-locale-dir(rtl) {
   transform: scaleX(-1);
 }
 
 .textbox-search-icon[searchbutton]:not([disabled]) {
   cursor: pointer;
@@ -57,23 +59,21 @@ html {
 .textbox-search-clear:not([disabled]) {
   cursor: default;
 }
 
 .textbox-search-icon:not([disabled]) {
   cursor: text;
 }
 
-.textbox-search-clear:not([disabled]):hover ,
-.textbox-search-icon:not([disabled]):hover {
+.textbox-search-clear:not([disabled]):hover {
   background-position: -16px 0;
 }
 
-.textbox-search-clear:not([disabled]):hover:active ,
-.textbox-search-icon:not([disabled]):hover:active {
+.textbox-search-clear:not([disabled]):hover:active {
   background-position: -32px 0;
 }
 
 .client .item.tab > .item-title-container {
   padding-inline-start: 26px;
 }
 .item.tab > .item-title-container {
   padding-inline-start: 14px;