diff --git a/client/src/cmdhfmf.c b/client/src/cmdhfmf.c
index e5ab53d66..51a9a13f0 100644
--- a/client/src/cmdhfmf.c
+++ b/client/src/cmdhfmf.c
@@ -6212,7 +6212,7 @@ int CmdHFMFNDEFWrite(const char *Cmd) {
     uint8_t freemem[MIFARE_4K_MAXSECTOR] = {0};
     uint16_t sum = 0;
     uint8_t block_no = 0;
-    for (uint8_t i = 1; i < madlen; i++) {
+    for (uint8_t i = 1; i < (madlen & 0xFF); i++) {
 
         freemem[i] = (mad[i] == NDEF_MFC_AID);