diff --git a/Ambiance/gtk-3.0/gtk-widgets.css b/Ambiance/gtk-3.0/gtk-widgets.css
--- a/Ambiance/gtk-3.0/gtk-widgets.css
+++ b/Ambiance/gtk-3.0/gtk-widgets.css
@@ -1869,16 +1869,17 @@ GtkTextView {
 
 /***********
  * tooltip *
  ***********/
 .tooltip {
     background-image: -gtk-gradient (radial, center 0, 0, center 0, 0.8,
                                      from (alpha (mix (@tooltip_bg_color, #ffffff, 0.2), 0.86)),
                                      to (alpha (@tooltip_bg_color, 0.86)));
+    background-color: @tooltip_bg_color;
     border-color: alpha (#ffffff, 0.2);
     border-radius: 5px;
     border-style: solid;
     border-width: 1px;
 
     color: @tooltip_fg_color;
 }
 
diff --git a/Radiance/gtk-3.0/gtk-widgets.css b/Radiance/gtk-3.0/gtk-widgets.css
--- a/Radiance/gtk-3.0/gtk-widgets.css
+++ b/Radiance/gtk-3.0/gtk-widgets.css
@@ -1866,16 +1866,17 @@ GtkTextView {
 
 /***********
  * tooltip *
  ***********/
 .tooltip {
     background-image: -gtk-gradient (radial, center 0, 0, center 0, 0.8,
                                      from (alpha (mix (@tooltip_bg_color, #ffffff, 0.2), 0.86)),
                                      to (alpha (@tooltip_bg_color, 0.86)));
+    background-color: @tooltip_bg_color;
     border-color: alpha (#ffffff, 0.2);
     border-radius: 5px;
     border-style: solid;
     border-width: 1px;
 
     color: @tooltip_fg_color;
 }