diff --git a/src/main/java/org/simplify4u/plugins/PublicKeyUtils.java b/src/main/java/org/simplify4u/plugins/PublicKeyUtils.java
index 77e1053f..9a07e976 100644
--- a/src/main/java/org/simplify4u/plugins/PublicKeyUtils.java
+++ b/src/main/java/org/simplify4u/plugins/PublicKeyUtils.java
@@ -173,17 +173,20 @@ private static void verifyPublicKeyRing(PGPPublicKeyRing publicKeyRing) {
 
     private static void verifySigForSubKey(PGPPublicKey subKey, PGPPublicKeyRing publicKeyRing) {
 
-        subKey.getSignatures().forEachRemaining(s -> Try.run(() -> {
+        subKey.getSignaturesOfType(PGPSignature.SUBKEY_BINDING).forEachRemaining(s -> Try.run(() -> {
                     PGPSignature sig = (PGPSignature) s;
                     PGPPublicKey masterKey = publicKeyRing.getPublicKey(sig.getKeyID());
                     if (masterKey != null) {
                         sig.init(new BcPGPContentVerifierBuilderProvider(), masterKey);
                         if (!sig.verifyCertification(masterKey, subKey)) {
                             throw new PGPException(
-                                    String.format("Failed signature type: %d for subKey: %s in key: %s",
+                                    String.format("Failed signature type: %x for subKey: %s in key: %s",
                                             sig.getSignatureType(),
                                             fingerprint(subKey), fingerprint(masterKey)));
                         }
+                    } else {
+                        throw new PGPException(String.format("Signature type: %x Not found key 0x%016X for subKeyId: %s",
+                                sig.getSignatureType(), sig.getKeyID(), fingerprint(subKey)));
                     }
                 }).get()
         );
diff --git a/src/test/java/org/simplify4u/plugins/PublicKeyUtilsTest.java b/src/test/java/org/simplify4u/plugins/PublicKeyUtilsTest.java
index 18dde083..51b423c7 100644
--- a/src/test/java/org/simplify4u/plugins/PublicKeyUtilsTest.java
+++ b/src/test/java/org/simplify4u/plugins/PublicKeyUtilsTest.java
@@ -121,7 +121,7 @@ public void invalidUTF8InUserId() throws IOException, PGPException {
     }
 
     @Test
-    public void invalidDerbyClient() throws IOException, PGPException {
+    public void validateSubKeyWithExternalSignature() throws IOException, PGPException {
 
         try (InputStream inputStream = getClass().getResourceAsStream("/3D8B00E198E21827.asc")) {
             PGPPublicKeyRing publicKeyRing = PublicKeyUtils.loadPublicKeyRing(inputStream, 0x3D8B00E198E21827L);