diff --git a/sys/init/3.sys.lua b/sys/init/3.sys.lua
index e8103d4..5a5583a 100644
--- a/sys/init/3.sys.lua
+++ b/sys/init/3.sys.lua
@@ -42,5 +42,5 @@ end
 
 -- non-standard - will raise error instead
 os.exit = function(code)
-	error(code)
+	error(code or 0)
 end
diff --git a/sys/modules/opus/event.lua b/sys/modules/opus/event.lua
index 5560beb..cd57b0f 100644
--- a/sys/modules/opus/event.lua
+++ b/sys/modules/opus/event.lua
@@ -60,7 +60,7 @@ function Routine:resume(event, ...)
 		end
 
 		if not s and event ~= 'terminate' then
-			if m and debug and debug.traceback then
+			if m and type(debug) == 'table' and debug.traceback then
 				local t = (debug.traceback(self.co, 1)) or ''
 				m = m .. '\n' .. t:match('%d\n(.+)')
 			end
diff --git a/sys/modules/opus/injector.lua b/sys/modules/opus/injector.lua
index 17a17f1..266d5a8 100644
--- a/sys/modules/opus/injector.lua
+++ b/sys/modules/opus/injector.lua
@@ -1,3 +1,5 @@
+-- https://www.lua.org/manual/5.1/manual.html#pdf-require
+
 local function split(str, pattern)
 	local t = { }
 	local function helper(line) table.insert(t, line) return "" end
@@ -65,14 +67,14 @@ return function(env)
 			local sPath = string.gsub(pattern, "%?", fname)
 			-- TODO: if there's no shell, we should not be checking relative paths below
 			-- as they will resolve to root directory
-			if env.shell and
-				type(env.shell.getRunningProgram) == 'function' and
-				sPath:sub(1, 1) ~= "/" then
+			if env.shell
+				and type(env.shell.getRunningProgram) == 'function'
+				and sPath:sub(1, 1) ~= "/" then
 
 				sPath = fs.combine(fs.getDir(env.shell.getRunningProgram() or ''), sPath)
 			end
 			if fs.exists(sPath) and not fs.isDir(sPath) then
-				return loadfile(sPath, env)
+				return loadfile(fs.combine(sPath, ''), env)
 			end
 		end
 	end
diff --git a/sys/modules/opus/trace.lua b/sys/modules/opus/trace.lua
index ed2738a..8f669d2 100644
--- a/sys/modules/opus/trace.lua
+++ b/sys/modules/opus/trace.lua
@@ -78,8 +78,6 @@ local function trim_traceback(stack)
 end
 
 return function (fn, ...)
-	-- xpcall in Lua 5.1 does not accept parameters
-	-- which is not ideal
 	local args = { ... }
 	local res = table.pack(xpcall(function()
 		return fn(table.unpack(args))
@@ -88,6 +86,10 @@ return function (fn, ...)
 	if not res[1] and res[2] ~= nil then
 		local err, trace = trim_traceback(res[2])
 
+		if err:match(':%d+: 0$') then
+			return true
+		end
+
 		if #trace > 0 then
 			_G._syslog('\n' .. err .. '\n' .. 'stack traceback:')
 			for _, v in ipairs(trace) do
@@ -95,10 +97,6 @@ return function (fn, ...)
 			end
 		end
 
-		if err:match(':%d+: 0$') then
-			return true
-		end
-
 		return res[1], err, trace
 	end
 
diff --git a/sys/modules/opus/ui/components/Button.lua b/sys/modules/opus/ui/components/Button.lua
index 426d3e0..f7f339c 100644
--- a/sys/modules/opus/ui/components/Button.lua
+++ b/sys/modules/opus/ui/components/Button.lua
@@ -19,6 +19,8 @@ UI.Button.defaults = {
 		[ ' ' ] = 'button_activate',
 		enter = 'button_activate',
 		mouse_click = 'button_activate',
+		mouse_doubleclick = 'button_activate',
+		mouse_tripleclick = 'button_activate',
 	}
 }
 function UI.Button:layout()