diff --git a/client/cmdhfmf.c b/client/cmdhfmf.c
index 997cf1275..0851cbf7d 100644
--- a/client/cmdhfmf.c
+++ b/client/cmdhfmf.c
@@ -340,7 +340,7 @@ int usage_hf14_nack(void) {
 	return 0;
 }
 
-int GetHFMF14AUID(uint8_t *uid) {
+int GetHFMF14AUID(uint8_t *uid, int *uidlen) {
 	UsbCommand c = {CMD_READER_ISO_14443a, {ISO14A_CONNECT | ISO14A_NO_DISCONNECT, 0, 0}};
 	clearCommandBuffer();
 	SendCommand(&c);
@@ -355,25 +355,23 @@ int GetHFMF14AUID(uint8_t *uid) {
 	iso14a_card_select_t card;
 	memcpy(&card, (iso14a_card_select_t *)resp.d.asBytes, sizeof(iso14a_card_select_t));
 	memcpy(uid, card.uid, card.uidlen * sizeof(uint8_t));
+	*uidlen=card.uidlen;
 	return 1;
 }
 
 char * GenerateFilename(const char *prefix, const char *suffix){
-	uint8_t uid[4] = {0,0,0,0};	
-	int len=0;
+	uint8_t uid[8] = {0,0,0,0,0,0,0,0};
+	int uidlen=0;
 	char * fptr = malloc (sizeof (char) * (strlen(prefix) + strlen(suffix)) + sizeof(uid)*2 + 1);
 	
-	if (!GetHFMF14AUID(uid)) {
+	if (!GetHFMF14AUID(uid, &uidlen)) {
 		PrintAndLog("No tag found.");
 		return NULL;
 	}
 	
-	strcpy(fptr, prefix);
-	len=strlen(fptr);
-	for (int i=0;i<sizeof(uid)/sizeof(uint8_t);i++)
-	len += sprintf(fptr+len, "%02x", uid[i]);	
-	strcat(fptr, suffix);
-
+	strcpy(fptr, prefix);	
+	FillFileNameByUID(fptr,uid,suffix,uidlen);
+	
 	return fptr;
 }
 
diff --git a/client/util.c b/client/util.c
index 35cd0cba0..8af798e4a 100644
--- a/client/util.c
+++ b/client/util.c
@@ -101,17 +101,19 @@ void AddLogCurrentDT(char *fn) {
 // param *uid  -  pointer to uid byte array
 // param *ext  -  ".log"
 // param uidlen - length of uid array.
-void FillFileNameByUID(char *fn, uint8_t *uid, char *ext, int uidlen) {
-	if ( fn == NULL || uid == NULL || ext == NULL ){
+void FillFileNameByUID(char *filenamePrefix, uint8_t *uid, const char *ext, int uidlen) {
+	if ( filenamePrefix == NULL || uid == NULL || ext == NULL ){
 		printf("[!] error parameter is NULL\n");
 		return;
 	}
-	char *fnameptr = fn;
-	memset(fn, 0x00, FILE_PATH_SIZE);
 	
-	for (int j = 0; j < uidlen; j++, fnameptr += 2)
-		sprintf(fnameptr, "%02X", uid[j]); 
-	sprintf(fnameptr, "%s", ext); 
+	int len=0;
+	len=strlen(filenamePrefix);
+	//memset(fn, 0x00, FILE_PATH_SIZE);
+	
+	for (int j = 0; j < uidlen; j++)
+		sprintf(filenamePrefix + len + j * 2, "%02X", uid[j]); 
+	strcat(filenamePrefix, ext); 
 }
 
 void hex_to_buffer(const uint8_t *buf, const uint8_t *hex_data, const size_t hex_len, const size_t hex_max_len, 
diff --git a/client/util.h b/client/util.h
index daf52c495..4b670b16a 100644
--- a/client/util.h
+++ b/client/util.h
@@ -174,7 +174,7 @@ extern void AddLogLine(char *fileName, char *extData, char *c);
 extern void AddLogHex(char *fileName, char *extData, const uint8_t * data, const size_t len);
 extern void AddLogUint64(char *fileName, char *extData, const uint64_t data);
 extern void AddLogCurrentDT(char *fileName);
-extern void FillFileNameByUID(char *fileName, uint8_t * uid, char *ext, int byteCount);
+extern void FillFileNameByUID(char *fileName, uint8_t * uid, const char *ext, int uidlen);
 
 extern void hex_to_buffer(const uint8_t *buf, const uint8_t *hex_data, const size_t hex_len, 
 						  const size_t hex_max_len, const size_t min_str_len, const size_t spaces_between,