diff --git a/builder/builder.lua b/builder/builder.lua
index a41677f..a2a5138 100644
--- a/builder/builder.lua
+++ b/builder/builder.lua
@@ -737,7 +737,7 @@ end
 --[[-- startup logic --]]--
 local args = {...}
 if #args < 1 then
-	error('supply file name')
+	error('supply file name or URL')
 end
 
 Builder.itemAdapter = Adapter.wrap({ side = 'bottom', direction = 'up' })
diff --git a/milo/plugins/remote/setup.lua b/milo/plugins/remote/setup.lua
index 10dfd7c..3ba5439 100644
--- a/milo/plugins/remote/setup.lua
+++ b/milo/plugins/remote/setup.lua
@@ -70,7 +70,9 @@ function setup:eventHandler(event)
 			if not fs.exists(STARTUP_FILE) then
 				Util.writeFile(STARTUP_FILE,
 					[[os.sleep(1)
-shell.openForegroundTab('packages/milo/MiloRemote')]])
+if shell.openForegroundTab then
+	shell.openForegroundTab('packages/milo/MiloRemote')
+end]])
 			end
 		elseif fs.exists(STARTUP_FILE) then
 			fs.delete(STARTUP_FILE)
diff --git a/swshop/w.lua b/swshop/w.lua
index 9b25fe7..85fadf7 100644
--- a/swshop/w.lua
+++ b/swshop/w.lua
@@ -72,14 +72,14 @@ function init(jua)
 	if async then
 		jua.on("websocket_success", function(event, url, handle)
 			local success, id = pcall(findID,url)
-			if id and callbackRegistry[id] and callbackRegistry[id].success then
+			if success and id and callbackRegistry[id] and callbackRegistry[id].success then
 				callbackRegistry[id].success(id, handle)
 			end
 		end)
 
 		jua.on("websocket_failure", function(event, url)
 			local success, id = pcall(findID,url)
-			if id and callbackRegistry[id] and callbackRegistry[id].failure then
+			if success and id and callbackRegistry[id] and callbackRegistry[id].failure then
 				callbackRegistry[id].failure(id)
 			end
 			table.remove(callbackRegistry, id)
@@ -87,14 +87,14 @@ function init(jua)
 
 		jua.on("websocket_message", function(event, url, data)
 			local success, id = pcall(findID,url)
-			if id and callbackRegistry[id] and callbackRegistry[id].message then
+			if success and id and callbackRegistry[id] and callbackRegistry[id].message then
 				callbackRegistry[id].message(id, data)
 			end
 		end)
 
 		jua.on("websocket_closed", function(event, url)
 			local success, id = pcall(findID,url)
-			if id and callbackRegistry[id] and callbackRegistry[id].closed then
+			if success and id and callbackRegistry[id] and callbackRegistry[id].closed then
 				callbackRegistry[id].closed(id)
 			end
 			table.remove(callbackRegistry, id)