diff --git a/init_functions.sh b/init_functions.sh
index f06f6c1..3e0f77c 100644
--- a/init_functions.sh
+++ b/init_functions.sh
@@ -110,7 +110,7 @@ install_os() {
 # detee_ghu stands for GitHub user and expects format detee_ghu=ghe0
 github_ssh_key() {
   local key=''
-  github_user=$(cat /proc/cmdline | grep -oE 'detee_ghu=[0-9a-z\_\.\-]+' | cut -d '=' -f2)
+  github_user=$(cat /proc/cmdline | grep -oE 'detee_ghu=[0-9a-zA-Z\_\.\-]+' | cut -d '=' -f2)
   [[ -z "$github_user" ]] && return 0
   mkdir -p /mnt/root/.ssh
   cd /mnt/root/.ssh