Weird behaviour of cobra/viper when binding flags to rootCmd

This (everything in the main.go) works

var rootCmd = &cobra.Command{
	Use:           "myapp",
	Short:         "Myapp",
	PreRunE: func(cmd *cobra.Command, args []string) error {
		fmt.Println("binding variables")
		if err := viper.BindPFlags(cmd.Flags()); err != nil {
			return err
		}
		fmt.Println(viper.GetString("allow-origin"))
		return nil
	},
	RunE: func(cmd *cobra.Command, args []string) error {
		return viper.BindPFlags(cmd.Flags())
	},
}

func main() {

	rootCmd.PersistentFlags().StringP("allow-origin", "", "", "help")

	rootCmd.Execute()
▶ go run web/main.go myapp --allow-origin https://111.222.33.4
binding variables
https://111.222.33.4

THIS, where the definition of the rootCmd and the flag addition has been moved to another package (cmd) does not work


package main

func main() {

	cmd.RootCmd.PersistentFlags().StringP("allow-origin", "", "", "help")


	cmd.RootCmd.Execute()
package cmd

var RootCmd = &cobra.Command{
	Use:           "myapp",
	Short:         "Myapp",
	PreRunE: func(cmd *cobra.Command, args []string) error {
		fmt.Println("binding variables")
		if err := viper.BindPFlags(cmd.Flags()); err != nil {
			return err
		}
		fmt.Println(viper.GetString("allow-origin"))
		return nil
	},
	RunE: func(cmd *cobra.Command, args []string) error {
		return viper.BindPFlags(cmd.Flags())
	},
}
▶ go run web/main.go myapp --allow-origin https://111.222.33.4
binding variables

i.e. in the second case, the flag allow-origin is not bound (!)

What am I missing?