iMX6UL U-Boot in debug mode

I’m modifying u-boot on my ccimx6ulsbv and compiled it with “#define Debug”. The debug output was printed but further u-boot updates failed with

Writing bootstream…/board/digi/common/cmd_bootstream/ncb.c:373: fcb_encrypt: Assertion `version == 1’ failed.

In this method @assert(version == 1):

int fcb_encrypt(BCB_ROM_BootBlockStruct_t *fcb, void *target, size_t size, int version)
uint32_t accumulator;
uint8_t *p;
uint8_t *q;

// Check for nonsense.

assert(version == 1);
assert(size >= sizeof(BCB_ROM_BootBlockStruct_t));

Checking the source I found the following usages of this method:

r = fcb_encrypt(&bootblock->fcb, bootblock->buf, size, 1);
r = fcb_encrypt(&bootblock->fcb, bootblock->buf, size, 3);

So I guess that in Debug mode the second call will always fail?!