'frequency_t' has not been declared

Hi, i got a problem with this code (sorry for my english)

I'm triying to declare this enum at the beginning of the program

enum frecuency_t { CLK_1MHZ, CLK_2MHZ, CLK_2DOT5MHZ, CLK_4MHZ, CLK_NO_CLK};

and when i tried to use it in the next lines

uint16_t activate(uint8_t* buf, uint16_t buf_size, frequency_t frequency=CLK_1MHZ); inside of a class

says that error

i've been triying to put inside the class but it's the same
whan i'm doing wrong?

is it :

frecuency_t

or

frequency_t

?

Also be aware that error sometimes comes up when people try to rely on the IDE to put in their function prototypes for them and it puts them in the wrong place. If you put those in yourself that error goes away.