diff --git a/libnfc/chips/pn53x.c b/libnfc/chips/pn53x.c
index 362cb4a..c961b46 100644
--- a/libnfc/chips/pn53x.c
+++ b/libnfc/chips/pn53x.c
@@ -317,9 +317,9 @@ pn53x_set_parameters(struct nfc_device *pnd, const uint8_t ui8Parameter, const b
 int
 pn53x_set_tx_bits(struct nfc_device *pnd, const uint8_t ui8Bits)
 {
-  int res = 0;
   // Test if we need to update the transmission bits register setting
   if (CHIP_DATA(pnd)->ui8TxBits != ui8Bits) {
+    int res = 0;
     // Set the amount of transmission bits in the PN53X chip register
     if ((res = pn53x_write_register(pnd, PN53X_REG_CIU_BitFraming, SYMBOL_TX_LAST_BITS, ui8Bits)) < 0)
       return res;
@@ -613,8 +613,8 @@ pn53x_WriteRegister(struct nfc_device *pnd, const uint16_t ui16RegisterAddress,
 int
 pn53x_write_register(struct nfc_device *pnd, const uint16_t ui16RegisterAddress, const uint8_t ui8SymbolMask, const uint8_t ui8Value)
 {
-  int res = 0;
   if ((ui16RegisterAddress < PN53X_CACHE_REGISTER_MIN_ADDRESS) || (ui16RegisterAddress > PN53X_CACHE_REGISTER_MAX_ADDRESS)) {
+    int res = 0;
     // Direct write
     if (ui8SymbolMask != 0xff) {
       uint8_t ui8CurrentValue;
diff --git a/libnfc/drivers/pn532_uart.c b/libnfc/drivers/pn532_uart.c
index 4cbb9a5..f7b8867 100644
--- a/libnfc/drivers/pn532_uart.c
+++ b/libnfc/drivers/pn532_uart.c
@@ -489,8 +489,8 @@ error:
 int
 pn532_uart_ack(nfc_device *pnd)
 {
-  int res = 0;
   if (POWERDOWN == CHIP_DATA(pnd)->power_mode) {
+    int res = 0;
     if ((res = pn532_uart_wakeup(pnd)) < 0) {
       return res;
     }
diff --git a/libnfc/nfc.c b/libnfc/nfc.c
index 6fabdf9..dd511a1 100644
--- a/libnfc/nfc.c
+++ b/libnfc/nfc.c
@@ -353,9 +353,8 @@ nfc_list_devices(nfc_context *context, nfc_connstring connstrings[], const size_
     const struct nfc_driver_list *pndl = nfc_drivers;
     while (pndl) {
       const struct nfc_driver *ndr = pndl->driver;
-      size_t _device_found = 0;
       if ((ndr->scan_type == NOT_INTRUSIVE) || ((context->allow_intrusive_scan) && (ndr->scan_type == INTRUSIVE))) {
-        _device_found = ndr->scan(context, connstrings + (device_found), connstrings_len - (device_found));
+        size_t _device_found = ndr->scan(context, connstrings + (device_found), connstrings_len - (device_found));
         log_put(LOG_GROUP, LOG_CATEGORY, NFC_LOG_PRIORITY_DEBUG, "%ld device(s) found using %s driver", (unsigned long) _device_found, ndr->name);
         if (_device_found > 0) {
           device_found += _device_found;
diff --git a/utils/nfc-mfclassic.c b/utils/nfc-mfclassic.c
index 081be3b..a5ebfe4 100644
--- a/utils/nfc-mfclassic.c
+++ b/utils/nfc-mfclassic.c
@@ -175,7 +175,6 @@ authenticate(uint32_t uiBlock)
 {
   mifare_cmd mc;
   uint32_t uiTrailerBlock;
-  size_t  key_index;
 
   // Set the authentication information (uid)
   memcpy(mp.mpa.abtAuthUid, nt.nti.nai.abtUid + nt.nti.nai.szUidLen - 4, 4);
@@ -200,7 +199,7 @@ authenticate(uint32_t uiBlock)
       return true;
   } else {
     // Try to guess the right key
-    for (key_index = 0; key_index < num_keys; key_index++) {
+    for (size_t key_index = 0; key_index < num_keys; key_index++) {
       memcpy(mp.mpa.abtKey, keys + (key_index * 6), 6);
       if (nfc_initiator_mifare_cmd(pnd, mc, uiBlock, &mp)) {
         if (bUseKeyA)