diff --git a/captcha/experimental.sh b/captcha/experimental.sh
index ec794f5..70e7549 100755
--- a/captcha/experimental.sh
+++ b/captcha/experimental.sh
@@ -150,8 +150,8 @@ INSTRUCTIONS2="...en remplaçant chaque X par la somme"
 # ****************************************************************************
 
 MODULES=(CALCUL NOTIN REPLACE REVERSE)
-NMODULES=#MODULES[@]
-RMODULE=`seq 0 $((NMODULES-1)) | sort -R | head -n 1`
+NMODULES=
+RMODULE=`seq 0 $(( ${#MODULES[@]} - 1)) | sort -R | head -n 1`
 #eval "${MODULES[RMODULE]}"
 
 TEXT="$NEWINPUT"