diff --git a/golibs/commander/commander.go b/golibs/commander/commander.go
index cd202b3..8a4d0b0 100644
--- a/golibs/commander/commander.go
+++ b/golibs/commander/commander.go
@@ -29,8 +29,8 @@ func (c *Commander) Loader(L *lua.LState) int {
 }
 
 func (c *Commander) register(L *lua.LState) int {
-	cmdName := L.ToString(1)
-	cmd := L.ToFunction(2)
+	cmdName := L.CheckString(1)
+	cmd := L.CheckFunction(2)
 
 	c.Events.Emit("commandRegister", cmdName, cmd)
 
diff --git a/golibs/fs/fs.go b/golibs/fs/fs.go
index c2eb137..a1017a8 100644
--- a/golibs/fs/fs.go
+++ b/golibs/fs/fs.go
@@ -27,7 +27,7 @@ var exports = map[string]lua.LGFunction{
 }
 
 func cd(L *lua.LState) int {
-	path := L.ToString(1)
+	path := L.CheckString(1)
 
 	err := os.Chdir(strings.TrimSpace(path))
 	if err != nil {
@@ -41,7 +41,7 @@ func cd(L *lua.LState) int {
 }
 
 func mkdir(L *lua.LState) int {
-	dirname := L.ToString(1)
+	dirname := L.CheckString(1)
 
 	// TODO: handle error here
 	os.Mkdir(strings.TrimSpace(dirname), 0744)
@@ -50,7 +50,7 @@ func mkdir(L *lua.LState) int {
 }
 
 func stat(L *lua.LState) int {
-	path := L.ToString(1)
+	path := L.CheckString(1)
 
 	// TODO: handle error here
 	pathinfo, _ := os.Stat(path)
diff --git a/lua.go b/lua.go
index 192eaf9..5e9ae55 100644
--- a/lua.go
+++ b/lua.go
@@ -81,20 +81,20 @@ func LuaInit(confpath string) {
 }
 
 func hshprompt(L *lua.LState) int {
-	prompt = L.ToString(1)
+	prompt = L.CheckString(1)
 
 	return 0
 }
 
 func hshmlprompt(L *lua.LState) int {
-	multilinePrompt = L.ToString(1)
+	multilinePrompt = L.CheckString(1)
 
 	return 0
 }
 
 func hshalias(L *lua.LState) int {
-	alias := L.ToString(1)
-	source := L.ToString(2)
+	alias := L.CheckString(1)
+	source := L.CheckString(2)
 
 	aliases[alias] = source
 
@@ -102,7 +102,7 @@ func hshalias(L *lua.LState) int {
 }
 
 func hshappendPath(L *lua.LState) int {
-	path := L.ToString(1)
+	path := L.CheckString(1)
 
 	os.Setenv("PATH", os.Getenv("PATH") + ":" + path)