diff --git a/quartz/src/main/java/com/vitorpamplona/quartz/crypto/nip04/Nip04.kt b/quartz/src/main/java/com/vitorpamplona/quartz/crypto/nip04/Nip04.kt
index c9cb73a69..7ee60712b 100644
--- a/quartz/src/main/java/com/vitorpamplona/quartz/crypto/nip04/Nip04.kt
+++ b/quartz/src/main/java/com/vitorpamplona/quartz/crypto/nip04/Nip04.kt
@@ -154,6 +154,7 @@ class Nip04(
 
             fun isNIP04(encoded: String): Boolean {
                 val l = encoded.length
+                if (l < 28) return false
                 return encoded[l - 28] == '?' && encoded[l - 27] == 'i' && encoded[l - 26] == 'v' && encoded[l - 25] == '='
             }