diff --git a/labels.go b/labels.go
index f9faacfe..979fccbc 100644
--- a/labels.go
+++ b/labels.go
@@ -122,9 +122,10 @@ func Split(s string) []int {
 }
 
 // NextLabel returns the index of the start of the next label in the
-// string s starting at offset.
+// string s starting at offset. A negative offset will cause a panic.
 // The bool end is true when the end of the string has been reached.
 // Also see PrevLabel.
+
 func NextLabel(s string, offset int) (i int, end bool) {
 	if s == "" {
 		return 0, true