diff --git a/nixos/modules/services/networking/wpa_supplicant.nix b/nixos/modules/services/networking/wpa_supplicant.nix
index 08a17d20ed7f..395139879036 100644
--- a/nixos/modules/services/networking/wpa_supplicant.nix
+++ b/nixos/modules/services/networking/wpa_supplicant.nix
@@ -233,6 +233,9 @@ in {
       path = [ pkgs.wpa_supplicant ];
 
       script = ''
+        if [ -f /etc/wpa_supplicant.conf -a "/etc/wpa_supplicant.conf" != "${configFile}" ]
+        then echo >&2 "<3>/etc/wpa_supplicant.conf present but ignored. Generated ${configFile} is used instead."
+        fi
         iface_args="-s -u -D${cfg.driver} -c ${configFile}"
         ${if ifaces == [] then ''
           for i in $(cd /sys/class/net && echo *); do