diff --git a/fido2/ctap.c b/fido2/ctap.c
index 4e88dd6..f6be44e 100644
--- a/fido2/ctap.c
+++ b/fido2/ctap.c
@@ -777,7 +777,18 @@ int ctap_filter_invalid_credentials(CTAP_getAssertion * GA)
         if (! ctap_authenticate_credential(&GA->rp, &GA->creds[i]))
         {
             printf1(TAG_GA, "CRED #%d is invalid\n", GA->creds[i].credential.id.count);
-            GA->creds[i].credential.id.count = 0;      // invalidate
+#ifdef ENABLE_U2F_EXTENSIONS
+            if (is_extension_request((uint8_t*)&GA->creds[i].credential.id, sizeof(CredentialId)))
+            {
+                printf1(TAG_EXT, "CRED #%d is extension\n", GA->creds[i].credential.id.count);
+                count++;
+            }
+            else
+#endif
+            {
+                GA->creds[i].credential.id.count = 0;      // invalidate
+            }
+
         }
         else
         {
@@ -999,8 +1010,20 @@ uint8_t ctap_get_assertion(CborEncoder * encoder, uint8_t * request, int length)
     ret = cbor_encoder_create_map(encoder, &map, map_size);
     check_ret(ret);
 
-    ret = ctap_make_auth_data(&GA.rp, &map, auth_data_buf, sizeof(auth_data_buf), NULL, 0,0,NULL, 0);
-    check_retr(ret);
+#ifdef ENABLE_U2F_EXTENSIONS
+    if ( is_extension_request((uint8_t*)&GA.creds[validCredCount - 1].credential.id, sizeof(CredentialId)) )
+    {
+        ret = cbor_encode_int(&map,RESP_authData);
+        check_ret(ret);
+        ret = cbor_encode_byte_string(&map, auth_data_buf, sizeof(CTAP_authDataHeader));
+        check_ret(ret);
+    }
+    else
+#endif
+    {
+        ret = ctap_make_auth_data(&GA.rp, &map, auth_data_buf, sizeof(auth_data_buf), NULL, 0,0,NULL, 0);
+        check_retr(ret);
+    }
 
     /*for (int j = 0; j < GA.credLen; j++)*/
     /*{*/
diff --git a/fido2/extensions/extensions.c b/fido2/extensions/extensions.c
index 97bbe0a..d14cab8 100644
--- a/fido2/extensions/extensions.c
+++ b/fido2/extensions/extensions.c
@@ -82,7 +82,7 @@ int16_t extend_fido2(CredentialId * credid, uint8_t * output)
 {
     if (is_extension_request((uint8_t*)credid, sizeof(CredentialId)))
     {
-        bridge_u2f_to_solo(output, (uint8_t*)credid, sizeof(CredentialId));
+        output[0] = bridge_u2f_to_solo(output+1, (uint8_t*)credid, sizeof(CredentialId));
         return 1;
     }
     else
diff --git a/fido2/extensions/solo.c b/fido2/extensions/solo.c
index 4637b89..1a86422 100644
--- a/fido2/extensions/solo.c
+++ b/fido2/extensions/solo.c
@@ -31,7 +31,7 @@
 #include "log.h"
 #include APP_CONFIG
 
-// output must be at least 72 bytes
+// output must be at least 71 bytes
 int16_t bridge_u2f_to_solo(uint8_t * output, uint8_t * keyh, int keylen)
 {
     int8_t ret = 0;
diff --git a/tools/solotool.py b/tools/solotool.py
index aafe5f5..1573979 100755
--- a/tools/solotool.py
+++ b/tools/solotool.py
@@ -201,6 +201,24 @@ class SoloClient:
 
         return res.signature[1:]
 
+    def exchange_fido2(self, cmd, addr=0, data=b"A" * 16):
+        chal = "B" * 32
+
+        req = SoloClient.format_request(cmd, addr, data)
+
+        assertions, client_data = self.client.get_assertion(
+            self.host, chal, [{"id": req, "type": "public-key"}]
+        )
+        if len(assertions) < 1:
+            raise RuntimeError("Device didn't respond to FIDO2 extended assertion")
+
+        res = assertions[0]
+        ret = res.signature[0]
+        if ret != CtapError.ERR.SUCCESS:
+            raise RuntimeError("Device returned non-success code %02x" % (ret,))
+
+        return res.signature[1:]
+
     def bootloader_version(self,):
         data = self.exchange(SoloBootloader.version)
         if len(data) > 2:
@@ -208,7 +226,7 @@ class SoloClient:
         return data[0]
 
     def solo_version(self,):
-        data = self.exchange_u2f(SoloExtension.version)
+        data = self.exchange_fido2(SoloExtension.version)
         return (data[0], data[1], data[2])
 
     def write_flash(self, addr, data):
@@ -585,6 +603,7 @@ def solo_main():
         action="store_true",
         help="Continuously dump random numbers generated from Solo.",
     )
+
     parser.add_argument("--wink", action="store_true", help="HID Wink command.")
     parser.add_argument(
         "--reset",
@@ -596,6 +615,9 @@ def solo_main():
         action="store_true",
         help="Verify that the Solo firmware is from SoloKeys.  Check firmware version.",
     )
+    parser.add_argument(
+        "--version", action="store_true", help="Check firmware version on Solo."
+    )
     args = parser.parse_args()
 
     p = SoloClient()
@@ -627,6 +649,9 @@ def solo_main():
         else:
             print("Unknown fingerprint! ", cert.fingerprint(hashes.SHA256()))
 
+        args.version = True
+
+    if args.version:
         try:
             v = p.solo_version()
             print("Version: ", v)