diff --git a/frontend/ui/size.lua b/frontend/ui/size.lua
index ddb648583..5e968cfd2 100644
--- a/frontend/ui/size.lua
+++ b/frontend/ui/size.lua
@@ -64,6 +64,7 @@ local Size = {
         thin = Screen:scaleBySize(0.5),
         medium = Screen:scaleBySize(1),
         thick = Screen:scaleBySize(1.5),
+        focus_indicator = Screen:scaleBySize(5),
         progress = Screen:scaleBySize(7),
     },
     item = {
diff --git a/plugins/coverbrowser.koplugin/mosaicmenu.lua b/plugins/coverbrowser.koplugin/mosaicmenu.lua
index d7e253823..34b35946a 100644
--- a/plugins/coverbrowser.koplugin/mosaicmenu.lua
+++ b/plugins/coverbrowser.koplugin/mosaicmenu.lua
@@ -408,19 +408,24 @@ function MosaicMenuItem:init()
     -- for compatibility with keyboard navigation
     -- (which does not seem to work well when multiple pages,
     -- even with classic menu)
-    self.underline_h = 1 -- smaller than default (3), don't waste space
+    local underline_h = Size.line.focus_indicator
+    local underline_padding = Size.padding.tiny
     self._underline_container = UnderlineContainer:new{
         vertical_align = "top",
-        padding = 0,
+        padding = underline_padding,
         dimen = Geom:new{
             x = 0, y = 0,
             w = self.width,
-            h = self.height
+            h = self.height + underline_h + underline_padding,
         },
-        linesize = self.underline_h,
+        linesize = underline_h,
         -- widget : will be filled in self:update()
     }
     self[1] = self._underline_container
+    -- (This MosaicMenuItem will be taller than self.height, but will be put
+    -- in a Container with a fixed height=item_height, so it will overflow it
+    -- on the bottom, in the room made by item_margin=Screen:scaleBySize(10),
+    -- so we should ensure underline_h + underline_padding stays below that.)
 
     -- Remaining part of initialization is done in update(), because we may
     -- have to do it more than once if item not found in db
@@ -435,7 +440,7 @@ function MosaicMenuItem:update()
 
     local dimen = Geom:new{
         w = self.width,
-        h = self.height - self.underline_h
+        h = self.height,
     }
 
     -- We'll draw a border around cover images, it may not be