diff --git a/armsrc/iso14443a.c b/armsrc/iso14443a.c
index 67afee4f1..60023fe4d 100644
--- a/armsrc/iso14443a.c
+++ b/armsrc/iso14443a.c
@@ -2552,6 +2552,7 @@ void ReaderMifare(bool first_try, uint8_t block, uint8_t keytype ) {
 
 /*
 *  Mifare Classic NACK-bug detection
+*  Thanks to @doegox for the feedback and new approaches.
 */
 void DetectNACKbug() {
 
@@ -2571,6 +2572,7 @@ void DetectNACKbug() {
 	uint16_t sync_tries = 0;
 	uint32_t sync_time = 0;
 	bool have_uid = false;
+	bool received_nack;
 	
 	// Mifare Classic's random generator repeats every 2^16 cycles (and so do the nonces).			
 	uint32_t sync_cycles = PRNG_SEQUENCE_LENGTH;
@@ -2592,6 +2594,18 @@ void DetectNACKbug() {
 	uint16_t i;
 	for (i = 0; true; ++i) {
 
+		received_nack = false;
+		if ((i==10) && (num_nacks == i)) {
+			// Cards always leaks a NACK, no matter the parity
+			isOK = 2;
+			break;
+		}
+		if ( (i > 1) && (num_nacks == 1) ) {
+			// NACK bug
+			isOK = 1;
+			break;
+		}
+	
 		WDT_HIT();
 
 		// Test if the action was cancelled
@@ -2639,7 +2653,7 @@ void DetectNACKbug() {
 		// Receive the (4 Byte) "random" nonce from TAG
 		if (!ReaderReceive(receivedAnswer, receivedAnswerPar))
 			continue;
-
+	
 		previous_nt = nt;
 		nt = bytes_to_num(receivedAnswer, 4);
 		
@@ -2735,7 +2749,7 @@ void DetectNACKbug() {
 		// Receive answer. This will be a 4 Bit NACK when the 8 parity bits are OK after decoding
 		if (ReaderReceive(receivedAnswer, receivedAnswerPar)) {
 			catch_up_cycles = 8; 	// the PRNG is delayed by 8 cycles due to the NAC (4Bits = 0x05 encrypted) transfer	
-			isOK = 1;
+			received_nack = true;
 			num_nacks++;
 		} 
 
diff --git a/client/Makefile b/client/Makefile
index a53903dd6..b05845db1 100644
--- a/client/Makefile
+++ b/client/Makefile
@@ -212,7 +212,7 @@ MULTIARCHOBJS = $(MULTIARCHSRCS:%.c=$(OBJDIR)/%_NOSIMD.o) \
 
 #GCC_GTEQ_490 := $(shell expr `gcc --version | awk '/gcc/{print $$NF;}' | sed -e 's/\.\([0-9][0-9]\)/\1/g' -e 's/\.\([0-9]\)/0\1/g' -e 's/^[0-9]\{3,4\}$$/&00/'` \>= 40900)
 GCC_VERSION := $(shell gcc --version | awk '/gcc/{print $$NF;}' | sed -e 's/\-.*//g' -e 's/\.\([0-9][0-9]\)/\1/g' -e 's/\.\([0-9]\)/0\1/g' -e 's/^[0-9]\{3,4\}$$/&00/')
-CLANG_VERSION := $(shell gcc --version | awk '/Apple LLVM version/{print $$4;}' | sed -e -e 's/\-.*//g' 's/\.\([0-9][0-9]\)/\1/g' -e 's/\.\([0-9]\)/0\1/g' -e 's/^[0-9]\{3,4\}$$/&00/')
+CLANG_VERSION := $(shell gcc --version | awk '/Apple LLVM version/{print $$4;}' | sed -e 's/\-.*//g' -e 's/\.\([0-9][0-9]\)/\1/g' -e 's/\.\([0-9]\)/0\1/g' -e 's/^[0-9]\{3,4\}$$/&00/')
 ifneq ($(CLANG_VERSION), )
 	SUPPORTS_AVX512 :=  $(shell [ $(CLANG_VERSION) -ge 80000 ] && echo "True" )
 endif
diff --git a/client/cmdhfmf.c b/client/cmdhfmf.c
index 2f7cc4077..01fe70f60 100644
--- a/client/cmdhfmf.c
+++ b/client/cmdhfmf.c
@@ -321,6 +321,17 @@ int usage_hf14_csave(void){
 	PrintAndLog("       hf mf csave 4 o filename");
 	return 0;
 }
+int usage_hf14_nack(void) {
+	PrintAndLog("Test a mifare classic based card for the NACK bug.");
+	PrintAndLog("");	
+	PrintAndLog("Usage:  hf mf nack [h] [v]");
+	PrintAndLog("Options:");
+	PrintAndLog("       h             this help");
+	PrintAndLog("       v             verbose");
+	PrintAndLog("samples:");
+	PrintAndLog("       hf mf nack");
+	return 0;
+}
 
 int CmdHF14AMifare(const char *Cmd) {
 	uint8_t blockno = 0, key_type = MIFARE_AUTH_KEYA;
@@ -2851,43 +2862,15 @@ int CmdHf14AMfSetMod(const char *Cmd) {
 // Mifare NACK bug detection
 int CmdHf14AMfNack(const char *Cmd) {
 
-	UsbCommand c = {CMD_MIFARE_NACK_DETECT, {0, 0, 0}};
-	clearCommandBuffer();
-	SendCommand(&c);
-	UsbCommand resp;
+	bool verbose = false;
+	char ctmp = param_getchar(Cmd, 0);	
+	if ( ctmp == 'h' || ctmp == 'H' ) return usage_hf14_nack();
+	if ( ctmp == 'v' || ctmp == 'V' ) verbose = true;
+
+	if ( verbose )
+		PrintAndLog("Started testing card for NACK bug. Press key to abort");
 	
-	PrintAndLog("Started testing card for NACK bug");
-	
-	while (true) {
-		
-		printf(".");
-		fflush(stdout);
-		if (ukbhit()) {
-			int gc = getchar(); (void)gc;
-			return -1;
-			break;
-		}
-	
-		if (WaitForResponseTimeout(CMD_ACK, &resp, 2000)) {
-			int32_t ok = resp.arg[0];
-			uint32_t nacks = resp.arg[1];
-			uint32_t auths = resp.arg[2];
-			
-			PrintAndLog("\nNum of sent auth requestes : %u", auths);
-			PrintAndLog("Num of received NACK       : %u", nacks);
-			switch( ok ) {
-				case -1 : PrintAndLog("Button pressed. Aborted."); return 1;
-				case -2 : PrintAndLog("Card answers NACK, (most likely a clone)"); return 1;
-				case -3 : PrintAndLog("Card random number generator is not predictable)."); return 1;
-				case -4 : PrintAndLog("Card random number generator seems to be based on the wellknown");
-						  PrintAndLog("generating polynomial with 16 effective bits only, but shows unexpected behaviour."); return 1;
-				case  1 : PrintAndLog("Card has NACK bug."); return 1;
-				case  0 : PrintAndLog("Card has not NACK bug."); return 1;
-				default : PrintAndLog("  errorcode from device [%i]", ok); return 1;
-			}
-			break;
-		}
-	}
+	detect_classic_nackbug(verbose);
 	return 0;
 }
 
diff --git a/client/mifarehost.c b/client/mifarehost.c
index 3c234d288..1e1cce3b1 100644
--- a/client/mifarehost.c
+++ b/client/mifarehost.c
@@ -81,8 +81,7 @@ static uint32_t nonce2key(uint32_t uid, uint32_t nt, uint32_t nr, uint64_t par_i
 	return i;
 }
 
-int mfDarkside(uint8_t blockno, uint8_t key_type, uint64_t *key)
-{
+int mfDarkside(uint8_t blockno, uint8_t key_type, uint64_t *key) {
 	uint32_t uid = 0;
 	uint32_t nt = 0, nr = 0;
 	uint64_t par_list = 0, ks_list = 0;
@@ -852,15 +851,59 @@ bool detect_classic_prng(void){
 	uint32_t nonce = bytes_to_num(respA.d.asBytes, respA.arg[0]);
 	return validate_prng_nonce(nonce);
 }
-/* Detect Mifare Classic NACK bug */
-bool detect_classic_nackbug(void){
+/* Detect Mifare Classic NACK bug 
+
+returns:
+0 = error during test / aborted
+1 = has nack bug
+2 = has not nack bug
+3 = always leak nacks  (clones)
+*/
+int detect_classic_nackbug(bool verbose){
 	
-	// get nonce?
+	UsbCommand c = {CMD_MIFARE_NACK_DETECT, {0, 0, 0}};
+	clearCommandBuffer();
+	SendCommand(&c);
+	UsbCommand resp;
 	
-	// loop max 256 times, 
-	// fixed nonce, different parity every call
+	if ( verbose )
+		printf("Press pm3-button on the proxmark3 device to abort both proxmark3 and client.\n");
+		
+	while (true) {
+		
+		printf(".");
+		fflush(stdout);
+		if (ukbhit()) {
+			int gc = getchar(); (void)gc;
+			return -1;
+			break;
+		}
 	
-	return false;
+		if (WaitForResponseTimeout(CMD_ACK, &resp, 2000)) {
+			int32_t ok = resp.arg[0];
+			uint32_t nacks = resp.arg[1];
+			uint32_t auths = resp.arg[2];
+			if ( verbose ) {
+				PrintAndLog("\nNum of sent auth requests : %u", auths);
+				PrintAndLog("Num of received NACK      : %u", nacks);
+			}
+			switch( ok ) {
+				case -1 : if (verbose) PrintAndLog("Button pressed. Aborted."); return 0;
+				case -3 : if (verbose) PrintAndLog("Card random number generator is not predictable)."); return 0;
+				case -4 : if (verbose) {
+							PrintAndLog("Card random number generator seems to be based on the well-known generating polynomial");
+							PrintAndLog("with 16 effective bits only, but shows unexpected behavior, try again."); 
+							return 0;
+						}
+				case  2 : PrintAndLog("Card always leak NACK."); return 3;
+				case  1 : PrintAndLog("Card has NACK bug."); return 1;
+				case  0 : PrintAndLog("Card has not NACK bug."); return 2;
+				default : PrintAndLog("  errorcode from device [%i]", ok); return 0;
+			}
+			break;
+		}
+	}	
+	return 0;
 }
 /* try to see if card responses to "chinese magic backdoor" commands. */
 void detect_classic_magic(void) {
diff --git a/client/mifarehost.h b/client/mifarehost.h
index 19e963b44..3c58583dc 100644
--- a/client/mifarehost.h
+++ b/client/mifarehost.h
@@ -67,8 +67,6 @@ typedef struct {
 	//uint8_t foundKey[2];
 } icesector_t;
 
- 
-
 extern char logHexFileName[FILE_PATH_SIZE];
 
 extern int mfDarkside(uint8_t blockno, uint8_t key_type, uint64_t *key);
@@ -95,6 +93,6 @@ extern int saveTraceCard(void);
 extern int tryDecryptWord(uint32_t nt, uint32_t ar_enc, uint32_t at_enc, uint8_t *data, int len);
 
 extern bool detect_classic_prng(void);
-extern bool detect_classic_nackbug(void);
+extern int detect_classic_nackbug(bool verbose);
 extern void detect_classic_magic(void);
 #endif
\ No newline at end of file