Why can't I sys_write from a pointer to stack memory, using int 0x80?

Question

; NASM
push 30 ; '0'

mov rax, 4 ; write
mov rbx, 1 ; stdout
mov rcx, rsp ; ptr to character on stack
mov rdx, 1 ; length of string = 1
int 80h

The code above does not print anything to stdout. It works when i give it a ptr to a character in section .data. What am i doing wrong?