diff --git a/lib/nfc/protocols/mifare_classic.c b/lib/nfc/protocols/mifare_classic.c
index d2d7467dc..204e3a5eb 100644
--- a/lib/nfc/protocols/mifare_classic.c
+++ b/lib/nfc/protocols/mifare_classic.c
@@ -892,11 +892,25 @@ bool mf_classic_emulator(MfClassicEmulator* emulator, FuriHalNfcTxRxContext* tx_
             MfClassicSectorTrailer* sector_trailer =
                 (MfClassicSectorTrailer*)emulator->data.block[sector_trailer_block].value;
             if(cmd == MF_CLASSIC_AUTH_KEY_A_CMD) {
-                key = nfc_util_bytes2num(sector_trailer->key_a, 6);
-                access_key = MfClassicKeyA;
+                if(mf_classic_is_key_found(
+                       &emulator->data, mf_classic_get_sector_by_block(block), MfClassicKeyA)) {
+                    key = nfc_util_bytes2num(sector_trailer->key_a, 6);
+                    access_key = MfClassicKeyA;
+                } else {
+                    FURI_LOG_D(TAG, "Key not known");
+                    command_processed = true;
+                    break;
+                }
             } else {
-                key = nfc_util_bytes2num(sector_trailer->key_b, 6);
-                access_key = MfClassicKeyB;
+                if(mf_classic_is_key_found(
+                       &emulator->data, mf_classic_get_sector_by_block(block), MfClassicKeyB)) {
+                    key = nfc_util_bytes2num(sector_trailer->key_b, 6);
+                    access_key = MfClassicKeyB;
+                } else {
+                    FURI_LOG_D(TAG, "Key not known");
+                    command_processed = true;
+                    break;
+                }
             }
 
             uint32_t nonce = prng_successor(DWT->CYCCNT, 32) ^ 0xAA;