diff --git a/share/examples/jails/jib b/share/examples/jails/jib
--- a/share/examples/jails/jib
+++ b/share/examples/jails/jib
@@ -272,7 +272,7 @@
 	shift $(( $OPTIND - 1 ))
 
 	local name="$1"
-	[ "${name:-x}" = "${name#*[!0-9a-zA-Z_]}" -a $# -gt 1 ] ||
+	[ "${name:-x}" = "${name#*[![[:print:]]]}" -a $# -gt 1 ] ||
 		action_usage addm # NOTREACHED
 	shift 1 # name
 
@@ -382,7 +382,7 @@
 	done
 	shift $(( $OPTIND -1 ))
 	local name="$1"
-	[ "${name:-x}" = "${name#*[!0-9a-zA-Z_]}" -a $# -eq 1 ] ||
+	[ "${name:-x}" = "${name#*[![[:print:]]]}" -a $# -eq 1 ] ||
 		action_usage destroy # NOTREACHED
 	mustberoot_to_continue
 	jib_show "$name" | xargs -rn1 -I eiface ifconfig eiface destroy
diff --git a/share/examples/jails/jng b/share/examples/jails/jng
--- a/share/examples/jails/jng
+++ b/share/examples/jails/jng
@@ -275,7 +275,7 @@
 	shift $(( $OPTIND - 1 ))
 
 	local name="$1"
-	[ "${name:-x}" = "${name#*[!0-9a-zA-Z_]}" -a $# -gt 1 ] ||
+	[ "${name:-x}" = "${name#*[![[:print:]]]}" -a $# -gt 1 ] ||
 		action_usage bridge # NOTREACHED
 	shift 1 # name
 
@@ -443,7 +443,7 @@
 	done
 	shift $(( $OPTIND -1 ))
 	local name="$1"
-	[ "${name:-x}" = "${name#*[!0-9a-zA-Z_]}" -a $# -eq 1 ] ||
+	[ "${name:-x}" = "${name#*[![[:print:]]]}" -a $# -eq 1 ] ||
 		action_usage shutdown # NOTREACHED
 	mustberoot_to_continue
 	jng_show "$name" | xargs -rn1 -I eiface ngctl shutdown eiface:
@@ -461,7 +461,7 @@
 	done
 	shift $(( $OPTIND -1 ))
 	local name="$1"
-	[ "${name:-x}" = "${name#*[!0-9a-zA-Z_]}" -a $# -eq 1 ] ||
+	[ "${name:-x}" = "${name#*[![[:print:]]]}" -a $# -eq 1 ] ||
 		action_usage stats # NOTREACHED
 	mustberoot_to_continue
 	for eiface in $( jng_show "$name" ); do