diff --git a/sys/tools/makesyscalls.lua b/sys/tools/makesyscalls.lua
index 64b260eb65b..7824a533e4d 100644
--- a/sys/tools/makesyscalls.lua
+++ b/sys/tools/makesyscalls.lua
@@ -95,28 +95,30 @@ local files = {}
 
 local function cleanup()
 	for _, v in pairs(files) do
-		v:close()
+		assert(v:close())
 	end
 	if cleantmp then
 		if lfs.dir(tmpspace) then
 			for fname in lfs.dir(tmpspace) do
 				if fname ~= "." and fname ~= ".." then
-					os.remove(tmpspace .. "/" .. fname))
+					assert(os.remove(tmpspace .. "/" ..
+					    fname))
 				end
 			end
 		end
 
 		if lfs.attributes(tmpspace) and not lfs.rmdir(tmpspace) then
-			io.stderr:write("Failed to clean up tmpdir: " ..
-			    tmpspace .. "\n")
+			assert(io.stderr:write("Failed to clean up tmpdir: " ..
+			    tmpspace .. "\n"))
 		end
 	else
-		io.stderr:write("Temp files left in " .. tmpspace .. "\n")
+		assert(io.stderr:write("Temp files left in " .. tmpspace ..
+		    "\n"))
 	end
 end
 
 local function abort(status, msg)
-	io.stderr:write(msg .. "\n")
+	assert(io.stderr:write(msg .. "\n"))
 	cleanup()
 	os.exit(status)
 end
@@ -208,14 +210,11 @@ local function process_config(file)
 	-- would need to sanitize the line for potentially special characters.
 	local line_expr = "^([%w%p]+%s*)=(%s*[`\"]?[^\"`]+[`\"]?)"
 
-	if file == nil then
+	if not file then
 		return nil, "No file given"
 	end
 
-	local fh = io.open(file)
-	if fh == nil then
-		return nil, "Could not open file"
-	end
+	local fh = assert(io.open(file))
 
 	for nextline in fh:lines() do
 		-- Strip any whole-line comments
@@ -262,7 +261,7 @@ local function process_config(file)
 		end
 	end
 
-	io.close(fh)
+	assert(io.close(fh))
 	return cfg
 end
 
@@ -291,7 +290,7 @@ local function grab_capenabled(file, open_fail_ok)
 		end
 	end
 
-	io.close(fh)
+	assert(io.close(fh))
 	return capentries
 end
 
@@ -369,8 +368,8 @@ local function read_file(tmpfile)
 	end
 
 	local fh = files[tmpfile]
-	fh:seek("set")
-	return fh:read("a")
+	assert(fh:seek("set"))
+	return assert(fh:read("a"))
 end
 
 local function write_line(tmpfile, line)
@@ -378,13 +377,13 @@ local function write_line(tmpfile, line)
 		print("Not found: " .. tmpfile)
 		return
 	end
-	files[tmpfile]:write(line)
+	assert(files[tmpfile]:write(line))
 end
 
 local function write_line_pfile(tmppat, line)
 	for k in pairs(files) do
 		if k:match(tmppat) ~= nil then
-			files[k]:write(line)
+			assert(files[k]:write(line))
 		end
 	end
 end
@@ -505,7 +504,7 @@ local function process_sysfile(file)
 		process_syscall_def(prevline)
 	end
 
-	io.close(fh)
+	assert(io.close(fh))
 	return capentries
 end
 
@@ -1108,7 +1107,7 @@ end
 -- Entry point
 
 if #arg < 1 or #arg > 2 then
-	abort(1, "usage: " .. arg[0] .. " input-file <config-file>")
+	error("usage: " .. arg[0] .. " input-file <config-file>")
 end
 
 local sysfile, configfile = arg[1], arg[2]
@@ -1116,13 +1115,7 @@ local sysfile, configfile = arg[1], arg[2]
 -- process_config either returns nil and a message, or a
 -- table that we should merge into the global config
 if configfile ~= nil then
-	local res, msg = process_config(configfile)
-
-	if res == nil then
-		-- Error... handle?
-		print(msg)
-		os.exit(1)
-	end
+	local res = assert(process_config(configfile))
 
 	for k, v in pairs(res) do
 		if v ~= config[k] then
@@ -1150,17 +1143,28 @@ process_compat()
 process_abi_flags()
 
 if not lfs.mkdir(tmpspace) then
-	abort(1, "Failed to create tempdir " .. tmpspace)
+	error("Failed to create tempdir " .. tmpspace)
 end
 
+-- XXX Revisit the error handling here, we should probably move the rest of this
+-- into a function that we pcall() so we can catch the errors and clean up
+-- gracefully.
 for _, v in ipairs(temp_files) do
 	local tmpname = tmpspace .. v
 	files[v] = io.open(tmpname, "w+")
+	-- XXX Revisit these with a pcall() + error handler
+	if not files[v] then
+		abort(1, "Failed to open temp file: " .. tmpname)
+	end
 end
 
 for _, v in ipairs(output_files) do
 	local tmpname = tmpspace .. v
 	files[v] = io.open(tmpname, "w+")
+	-- XXX Revisit these with a pcall() + error handler
+	if not files[v] then
+		abort(1, "Failed to open temp output file: " .. tmpname)
+	end
 end
 
 -- Write out all of the preamble bits
@@ -1358,12 +1362,12 @@ write_line("systrace", read_file("systraceret"))
 for _, v in ipairs(output_files) do
 	local target = config[v]
 	if target ~= "/dev/null" then
-		local fh = io.open(target, "w+")
+		local fh = assert(io.open(target, "w+"))
 		if fh == nil then
 			abort(1, "Failed to open '" .. target .. "'")
 		end
-		fh:write(read_file(v))
-		fh:close()
+		assert(fh:write(read_file(v)))
+		assert(fh:close())
 	end
 end