VHDL- Quartus II (Web Edition) - size of the constante of std_logic_vector type

Hello Everybody,

I would like using different constants of std_logic_vector type like that, because I want to using the numeric value :

constant VAL_MAX_COMPTEUR_2HZ 	: std_logic_vector(19 downto 0) := To_stdlogicvector(X"000011");

and if I change the size of the std_logic_vector at 21 bit, quartus indicates :

Error (10324): VHDL Expression error at Jongleur_main.vhd(72): expression "('0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','0','1','0','0','0','1')" has 24 elements ; expected 21 elements.

For me that indicates that a constant is not taller than 20bit.

But I don't arrive to find the explanation for that

In advance thank you to the reading and if you have an explanation.

Best Regards,

Amitié - Philippe