diff --git a/lib/wibox/layout/flex.lua b/lib/wibox/layout/flex.lua
index cef6b99ed..3d525d3e2 100644
--- a/lib/wibox/layout/flex.lua
+++ b/lib/wibox/layout/flex.lua
@@ -52,24 +52,24 @@ local flex = {}
 
 function flex:layout(_, width, height)
     local result = {}
-    local pos,spacing = 0, self._spacing
-    local num = #self.widgets
+    local pos,spacing = 0, self._private.spacing
+    local num = #self._private.widgets
     local total_spacing = (spacing*(num-1))
 
     local space_per_item
-    if self.dir == "y" then
+    if self._private.dir == "y" then
         space_per_item = height / num - total_spacing/num
     else
         space_per_item = width / num - total_spacing/num
     end
 
-    if self._max_widget_size then
-        space_per_item = math.min(space_per_item, self._max_widget_size)
+    if self._private.max_widget_size then
+        space_per_item = math.min(space_per_item, self._private.max_widget_size)
     end
 
-    for _, v in pairs(self.widgets) do
+    for _, v in pairs(self._private.widgets) do
         local x, y, w, h
-        if self.dir == "y" then
+        if self._private.dir == "y" then
             x, y = 0, util.round(pos)
             w, h = width, floor(space_per_item)
         else
@@ -81,8 +81,8 @@ function flex:layout(_, width, height)
 
         pos = pos + space_per_item + spacing
 
-        if (self.dir == "y" and pos-spacing >= height) or
-            (self.dir ~= "y" and pos-spacing >= width) then
+        if (self._private.dir == "y" and pos-spacing >= height) or
+            (self._private.dir ~= "y" and pos-spacing >= width) then
             break
         end
     end
@@ -99,39 +99,41 @@ function flex:fit(context, orig_width, orig_height)
     local used_in_other = 0
 
     -- Figure out the maximum size we can give out to sub-widgets
-    local sub_height = self.dir == "x" and orig_height or orig_height / #self.widgets
-    local sub_width  = self.dir == "y" and orig_width  or orig_width / #self.widgets
+    local sub_height = self._private.dir == "x" and orig_height or orig_height / #self._private.widgets
+    local sub_width  = self._private.dir == "y" and orig_width  or orig_width / #self._private.widgets
 
-    for _, v in pairs(self.widgets) do
+    for _, v in pairs(self._private.widgets) do
         local w, h = base.fit_widget(self, context, v, sub_width, sub_height)
 
-        local max = self.dir == "y" and w or h
+        local max = self._private.dir == "y" and w or h
         if max > used_in_other then
             used_in_other = max
         end
 
-        used_in_dir = used_in_dir + (self.dir == "y" and h or w)
+        used_in_dir = used_in_dir + (self._private.dir == "y" and h or w)
     end
 
-    if self._max_widget_size then
+    if self._private.max_widget_size then
         used_in_dir = math.min(used_in_dir,
-            #self.widgets * self._max_widget_size)
+            #self._private.widgets * self._private.max_widget_size)
     end
 
-    local spacing = self._spacing * (#self.widgets-1)
+    local spacing = self._private.spacing * (#self._private.widgets-1)
 
-    if self.dir == "y" then
+    if self._private.dir == "y" then
         return used_in_other, used_in_dir + spacing
     end
     return used_in_dir + spacing, used_in_other
 end
 
---- Set the maximum size the widgets in this layout will take (that is,
--- maximum width for horizontal and maximum height for vertical).
--- @param val The maximum size of the widget.
+--- Set the maximum size the widgets in this layout will take.
+--That is, maximum width for horizontal and maximum height for vertical.
+-- @property max_widget_size
+-- @param number
+
 function flex:set_max_widget_size(val)
-    if self._max_widget_size ~= val then
-        self._max_widget_size = val
+    if self._private.max_widget_size ~= val then
+        self._private.max_widget_size = val
         self:emit_signal("widget::layout_changed")
     end
 end
@@ -139,9 +141,9 @@ end
 local function get_layout(dir, widget1, ...)
     local ret = fixed[dir](widget1, ...)
 
-    util.table.crush(ret, flex)
+    util.table.crush(ret, flex, true)
 
-    ret.fill_space = nil
+    ret._private.fill_space = nil
 
     return ret
 end
@@ -162,6 +164,10 @@ function flex.vertical(...)
     return get_layout("vertical", ...)
 end
 
+--@DOC_widget_COMMON@
+
+--@DOC_object_COMMON@
+
 return flex
 
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