diff --git a/ips.go b/ips.go
index 4986f51..23d9538 100644
--- a/ips.go
+++ b/ips.go
@@ -10,6 +10,9 @@ var p = regexp.MustCompile(`Failed password for .* from (.*) port`)
 
 // ParseIP finds the ip address from an sshd log line that contains a failed
 // password attempt.
+//
+// A found IP address will be returned; an empty string returned indicates
+// nothing was found.
 func ParseIP(line string) string {
 	if m := p.FindStringSubmatch(line); m != nil {
 		if len(m) != 2 {