diff --git a/digest.go b/digest.go
index d866b6b..3eaaf7a 100644
--- a/digest.go
+++ b/digest.go
@@ -80,7 +80,13 @@ func (da *DigestAuth) Purge(count int) {
 	}
 	cache := digestCache(entries)
 	sort.Sort(cache)
-	for _, client := range cache[:count] {
+
+	limit := count
+	if len(cache) < count {
+		limit = len(cache) - 1
+	}
+
+	for _, client := range cache[:limit] {
 		delete(da.clients, client.nonce)
 	}
 }