diff --git a/pico-keys-sdk b/pico-keys-sdk
index da3a7f2..f01aca5 160000
--- a/pico-keys-sdk
+++ b/pico-keys-sdk
@@ -1 +1 @@
-Subproject commit da3a7f25d0a7c5718d0288b2c3d369b9abee6049
+Subproject commit f01aca551893efa27137a9907289fa5bd442cfaa
diff --git a/src/fido/management.c b/src/fido/management.c
index 6bd299e..1827509 100644
--- a/src/fido/management.c
+++ b/src/fido/management.c
@@ -101,6 +101,7 @@ int man_get_config() {
     res_APDU[res_APDU_size++] = TAG_SERIAL;
     res_APDU[res_APDU_size++] = 4;
     memcpy(res_APDU + res_APDU_size, pico_serial.id, 4);
+    res_APDU[res_APDU_size] &= ~0xFC; // Force 8-digit serial number
     res_APDU_size += 4;
     res_APDU[res_APDU_size++] = TAG_FORM_FACTOR;
     res_APDU[res_APDU_size++] = 1;
diff --git a/src/fido/otp.c b/src/fido/otp.c
index 0e41dab..e434d27 100644
--- a/src/fido/otp.c
+++ b/src/fido/otp.c
@@ -476,6 +476,7 @@ int cmd_otp() {
     }
     else if (p1 == 0x10) {
         memcpy(res_APDU, pico_serial.id, 4);
+        res_APDU[0] &= ~0xFC; // Force 8-digit serial number
         res_APDU_size = 4;
     }
     else if (p1 == 0x13) { // Get config