diff --git a/sys/apis/ui.lua b/sys/apis/ui.lua
index f444c00..ead3543 100644
--- a/sys/apis/ui.lua
+++ b/sys/apis/ui.lua
@@ -1463,7 +1463,14 @@ function UI.Grid:update()
 		end
 	end
 
-	self.sorted = Util.keys(self.values)
+	self.sorted = { }
+	for k,v in pairs(self.values) do
+		if self:isRowValid(k, v) then
+			table.insert(self.sorted, k)
+		end
+	end
+
+	--self.sorted = Util.keys(self.values)
 	if order then
 		table.sort(self.sorted, function(a,b)
 			return order(self.values[a], self.values[b])
@@ -1545,6 +1552,12 @@ function UI.Grid:drawRows()
 	end
 end
 
+-- Non-intuitive: update must be called if the table was specified
+-- in the shortcut definition (as this callback was not yet overridden)
+function UI.Grid:isRowValid(--[[ key, value ]])
+	return true
+end
+
 function UI.Grid:getRowTextColor(row, selected)
 	if selected then
 		if self.focused then
@@ -2359,9 +2372,7 @@ function UI.Wizard:eventHandler(event)
 	elseif event.type == 'previousView' then
 		local currentView = Util.find(self.pages, 'enabled', true)
 		local nextView = Util.find(self.pages, 'index', currentView.index - 1)
-		if self:isViewValid() then
-			currentView:emit({ type = 'enable_view', prev = nextView, current = currentView })
-		end
+		currentView:emit({ type = 'enable_view', prev = nextView, current = currentView })
 		return true
 
 	elseif event.type == 'wizard_complete' then
diff --git a/sys/apis/util.lua b/sys/apis/util.lua
index eb50f58..41a3f1c 100644
--- a/sys/apis/util.lua
+++ b/sys/apis/util.lua
@@ -356,6 +356,7 @@ function Util.readFile(fname)
 end
 
 function Util.writeFile(fname, data)
+	if not fname or not data then error('Util.writeFile: invalid parameters', 2) end
 	local file = io.open(fname, "w")
 	if not file then
 		error('Unable to open ' .. fname, 2)
@@ -489,7 +490,7 @@ function Util.insertString(str, istr, pos)
 end
 
 function Util.split(str, pattern)
-	if not str then error('Util:split: invalid parameters', 2) end
+	if not str then error('Util.split: Invalid parameters', 2) end
 	pattern = pattern or "(.-)\n"
 	local t = {}
 	local function helper(line) table.insert(t, line) return "" end