diff --git a/browser/components/customizableui/src/CustomizableUI.jsm b/browser/components/customizableui/src/CustomizableUI.jsm
index f05c352d6ac6..07b5e6ec432c 100644
--- a/browser/components/customizableui/src/CustomizableUI.jsm
+++ b/browser/components/customizableui/src/CustomizableUI.jsm
@@ -316,13 +316,9 @@ let CustomizableUIInternal = {
         continue;
       }
 
-      if (aArea == CustomizableUI.AREA_PANEL) {
-        if (provider == CustomizableUI.PROVIDER_XUL) {
-          this.ensureButtonClosesPanel(node);
-        }
-        node.classList.add("panel-contents-button");
-      } else {
-        node.classList.remove("panel-contents-button");
+      if (provider == CustomizableUI.PROVIDER_XUL &&
+          aArea == CustomizableUI.AREA_PANEL) {
+        this.ensureButtonClosesPanel(node);
       }
       this.ensureButtonContextMenu(node, aArea == CustomizableUI.AREA_PANEL);
 
@@ -459,7 +455,6 @@ let CustomizableUIInternal = {
       if (!btn.hasAttribute("noautoclose")) {
         this.ensureButtonClosesPanel(btn);
       }
-      btn.classList.add("panel-contents-button");
       this.ensureButtonContextMenu(btn, true);
     }
 
@@ -493,13 +488,9 @@ let CustomizableUIInternal = {
       let container = areaNode.customizationTarget;
       let [provider, widgetNode] = this.getWidgetNode(aWidgetId, window);
 
-      if (aArea == CustomizableUI.AREA_PANEL) {
-        if (provider == CustomizableUI.PROVIDER_XUL) {
-          this.ensureButtonClosesPanel(widgetNode);
-        }
-        widgetNode.classList.add("panel-contents-button");
-      } else {
-        widgetNode.classList.remove("panel-contents-button");
+      if (provider == CustomizableUI.PROVIDER_XUL &&
+          aArea == CustomizableUI.AREA_PANEL) {
+        this.ensureButtonClosesPanel(widgetNode);
       }
 
       this.ensureButtonContextMenu(widgetNode, aArea == CustomizableUI.AREA_PANEL);
diff --git a/browser/themes/shared/customizableui/panelUIOverlay.inc.css b/browser/themes/shared/customizableui/panelUIOverlay.inc.css
index e4aac358fb18..cb1c8f2f21be 100644
--- a/browser/themes/shared/customizableui/panelUIOverlay.inc.css
+++ b/browser/themes/shared/customizableui/panelUIOverlay.inc.css
@@ -161,11 +161,6 @@ panelview:not([mainview]) .toolbarbutton-text,
   list-style-image: url(chrome://browser/skin/customizableui/menuPanel-small-icons.png);
 }
 
-.panel-contents-button[disabled] > .toolbarbutton-icon,
-.panel-combined-button[disabled] > .toolbarbutton-icon {
-  opacity: .5;
-}
-
 #PanelUI-contents[type="grid"] toolbarbutton > .toolbarbutton-icon,
 #customization-palette toolbarbutton > .toolbarbutton-icon {
   min-width: calc(8em / 3);