diff --git a/src/ZenGlanceManager.mjs b/src/ZenGlanceManager.mjs
index b1c4163..9c401bb 100644
--- a/src/ZenGlanceManager.mjs
+++ b/src/ZenGlanceManager.mjs
@@ -189,6 +189,7 @@
             this.lastCurrentTab.removeAttribute("zen-glance-tab");
               
             gBrowser.tabContainer._invalidateCachedTabs();
+            this.lastCurrentTab.closing = true;
             gBrowser.removeTab(this.lastCurrentTab, { animate: false });
 
             this.#currentTab = null;
diff --git a/src/ZenGradientGenerator.mjs b/src/ZenGradientGenerator.mjs
index 3242c21..807ec33 100644
--- a/src/ZenGradientGenerator.mjs
+++ b/src/ZenGradientGenerator.mjs
@@ -288,7 +288,7 @@
 
     async addCustomColor() {
       const color = this.customColorInput.value;
-      if (!color) {
+      if (!color || !color.match(/^#[0-9a-f]{3,6}$/i)) {
         return;
       }
       // can be any color format, we just add it to the list as a dot, but hidden