diff --git a/client/src/cmdhfmfu.c b/client/src/cmdhfmfu.c
index d56ae5123..1586d8bda 100644
--- a/client/src/cmdhfmfu.c
+++ b/client/src/cmdhfmfu.c
@@ -4392,6 +4392,10 @@ static int CmdHF14AMfUPwdGen(const char *Cmd) {
         if (u_len != 7 && u_len != 4) {
             PrintAndLogEx(WARNING, "Key must be 7 hex bytes");
             return PM3_EINVARG;
+        } else if (u_len == 4) {
+            // adapt to 7 bytes :)
+            memset(uid + 4, 0x00, 3);
+            u_len = 7;
         }
     }