diff --git a/exec.go b/exec.go
index ff4ace2..0e08cd5 100644
--- a/exec.go
+++ b/exec.go
@@ -192,8 +192,7 @@ func execCommand(cmd string, terminalOut bool) (io.Writer, io.Writer, error) {
 		if commands[args[0]] != nil {
 			luaexitcode, err := rt.Call1(l.MainThread(), rt.FunctionValue(commands[args[0]]), rt.TableValue(luacmdArgs))
 			if err != nil {
-				fmt.Fprintln(os.Stderr,
-					"Error in command:\n\n" + err.Error())
+				fmt.Fprintln(os.Stderr, "Error in command:\n\n" + err.Error())
 				return interp.NewExitStatus(1)
 			}
 
@@ -201,7 +200,11 @@ func execCommand(cmd string, terminalOut bool) (io.Writer, io.Writer, error) {
 
 			if code, ok := luaexitcode.TryInt(); ok {
 				exitcode = uint8(code)
-			} // TODO: deregister commander if return isnt number
+			} else if luaexitcode != rt.NilValue {
+				// deregister commander
+				delete(commands, args[0])
+				fmt.Fprintf(os.Stderr, "Commander did not return number for exit code. %s, you're fired.\n", args[0])
+			}
 
 			return interp.NewExitStatus(exitcode)
 		}