diff --git a/bin/can b/bin/can
index cad0270..8c4cdc7 100644
--- a/bin/can
+++ b/bin/can
@@ -15,7 +15,7 @@ if args.help or args.h then
 	print("Default options:")
 	for opt, val in pairs(candran.default) do
 		if type(val) == "string" then val = val:gsub("\n", "\\n") end
-		print(("  %s=%q"):format(opt, val))
+		print(("  %s=%q"):format(opt, tostring(val)))
 	end
 	return
 end
diff --git a/bin/canc b/bin/canc
index b87cb8f..32265ef 100644
--- a/bin/canc
+++ b/bin/canc
@@ -23,7 +23,7 @@ if #arg < 1 or args.help or args.h then
 	print("Default options:")
 	for opt, val in pairs(candran.default) do
 		if type(val) == "string" then val = val:gsub("\n", "\\n") end
-		print(("  %s=%q"):format(opt, val))
+		print(("  %s=%q"):format(opt, tostring(val)))
 	end
 	return
 end
diff --git a/candran.can b/candran.can
index 9e1d1fd..b203ab1 100644
--- a/candran.can
+++ b/candran.can
@@ -234,7 +234,7 @@ local codeCache = {}
 function candran.loadfile(filepath, env, options)
 	local f, err = io.open(filepath)
 	if not f then
-		return nil, "cannot open %s":format(err)
+		return nil, "cannot open %s":format(tostring(err))
 	end
 	local content = f:read("*a")
 	f:close()
@@ -352,7 +352,7 @@ function candran.searcher(modpath)
 		if r then
 			return r(modpath, filepath)
 		else
-			error("error loading candran module '%s' from file '%s':\n\t%s":format(modpath, filepath, s), 0)
+			error("error loading candran module '%s' from file '%s':\n\t%s":format(modpath, filepath, tostring(s)), 0)
 		end
 	end, filepath
 end