--- a/widget/gtk/nsLookAndFeel.cpp
+++ b/widget/gtk/nsLookAndFeel.cpp
@@ -78,16 +78,18 @@ GetLightAndDarkness(const GdkRGBA& aColo
 static bool
 GetGradientColors(const GValue* aValue,
                   GdkRGBA* aLightColor, GdkRGBA* aDarkColor)
 {
     if (!G_TYPE_CHECK_VALUE_TYPE(aValue, CAIRO_GOBJECT_TYPE_PATTERN))
         return false;
 
     auto pattern = static_cast<cairo_pattern_t*>(g_value_get_boxed(aValue));
+    if (!pattern)
+        return false;
 
     // Just picking the lightest and darkest colors as simple samples rather
     // than trying to blend, which could get messy if there are many stops.
     if (CAIRO_STATUS_SUCCESS !=
         cairo_pattern_get_color_stop_rgba(pattern, 0, nullptr, &aDarkColor->red,
                                           &aDarkColor->green, &aDarkColor->blue,
                                           &aDarkColor->alpha))
         return false;