diff --git a/applets/ctap/ctap.c b/applets/ctap/ctap.c
index 11d9ea6b..1f07d5d3 100644
--- a/applets/ctap/ctap.c
+++ b/applets/ctap/ctap.c
@@ -702,6 +702,7 @@ static uint8_t ctap_make_credential(CborEncoder *encoder, uint8_t *params, size_
     sha256_update(mc.client_data_hash, sizeof(mc.client_data_hash));
     sha256_final(data_buf);
     len = sign_with_device_key(data_buf, PRIVATE_KEY_LENGTH[SECP256R1], data_buf);
+    if (!len) return CTAP2_ERR_UNHANDLED_REQUEST;
     ret = cbor_encode_byte_string(&att_map, data_buf, len);
     CHECK_CBOR_RET(ret);
 
@@ -1154,6 +1155,7 @@ static uint8_t ctap_get_assertion(CborEncoder *encoder, uint8_t *params, size_t
   DBG_MSG("Message: ");
   PRINT_HEX(data_buf, len + CLIENT_DATA_HASH_SIZE);
   len = sign_with_private_key(dc.credential_id.alg_type, &key, data_buf, len + CLIENT_DATA_HASH_SIZE, data_buf);
+  if (len < 0) return CTAP2_ERR_UNHANDLED_REQUEST;
   DBG_MSG("Signature: ");
   PRINT_HEX(data_buf, len);
   ret = cbor_encode_byte_string(&map, data_buf, len);
diff --git a/applets/ctap/secret.c b/applets/ctap/secret.c
index a37c3a17..174ac95f 100644
--- a/applets/ctap/secret.c
+++ b/applets/ctap/secret.c
@@ -334,7 +334,7 @@ int verify_key_handle(const credential_id *kh, ecc_key_t *key) {
 size_t sign_with_device_key(const uint8_t *input, size_t input_len, uint8_t *sig) {
   ecc_key_t key;
   int ret = read_device_pri_key(key.pri);
-  if (ret < 0) return ret;
+  if (ret < 0) return 0;
   ecc_sign(SECP256R1, &key, input, input_len, sig);
   memzero(&key, sizeof(key));
   return ecdsa_sig2ansi(PRI_KEY_SIZE, sig, sig);
diff --git a/interfaces/NFC/fm.c b/interfaces/NFC/fm.c
index a94c8d44..669f8fb9 100644
--- a/interfaces/NFC/fm.c
+++ b/interfaces/NFC/fm.c
@@ -18,6 +18,8 @@ uint8_t fm_read_reg(uint16_t reg) {
   fm_csn_high();
 #elif NFC_CHIP == NFC_CHIP_FM11NT
   fm11nt_read(reg, &val, 1);
+#else
+  val = 0;
 #endif
   return val;
 }
diff --git a/interfaces/USB/class/webusb/webusb.c b/interfaces/USB/class/webusb/webusb.c
index 51b1c669..61bcca5f 100644
--- a/interfaces/USB/class/webusb/webusb.c
+++ b/interfaces/USB/class/webusb/webusb.c
@@ -69,7 +69,7 @@ uint8_t USBD_WEBUSB_Setup(USBD_HandleTypeDef *pdev, USBD_SetupReqTypedef *req) {
     break;
 
   case WEBUSB_REQ_STAT:
-    USBD_CtlSendData(pdev, &state, 1, WEBUSB_EP0_SENDER);
+    USBD_CtlSendData(pdev, (uint8_t*)&state, 1, WEBUSB_EP0_SENDER);
     break;
 
   default: