diff --git a/protonkey b/protonkey
index b52a616..4595cc5 100755
--- a/protonkey
+++ b/protonkey
@@ -1,7 +1,7 @@
 #!/bin/sh
 
 if ! test -n "$1"; then
-	printf "Usage: %s [ProtonMail address]" "$0"
+	printf "Usage: %s [ProtonMail address]\n" "$0"
 	exit 64 # syexits(3) EX_USAGE
 fi