diff --git a/src/zfs-auto-snapshot.sh b/src/zfs-auto-snapshot.sh
index d540819..44db629 100755
--- a/src/zfs-auto-snapshot.sh
+++ b/src/zfs-auto-snapshot.sh
@@ -256,7 +256,7 @@ do
 			while test "${#opt_prefix}" -gt '0'
 			do
 				case $opt_prefix in
-					([![:alnum:]_-.:\ ]*)
+					([![:alnum:]_.:\ -]*)
 						print_log error "The $1 parameter must be alphanumeric."
 						exit 130
 						;;
@@ -278,7 +278,7 @@ do
 			;;
 		(--sep)
 			case "$2" in 
-				([[:alnum:]_-.:\ ])
+				([[:alnum:]_.:\ -])
 					:
 					;;
 				('')