Random behavior using a wrapped C library

[simendsjo]

I'm getting some unexpected results (crashes or random behavior) when  
using a wrapped C struct in a library. I have no idea why this is  
happening as everything else (including other wrapped structs) seems to  
work just fine.
Could it be some alignment issues..?

extern(C):
//typedef unsigned char uint8;
alias ubyte uint8;

//typedef struct {
//      uint8 r,g,b;
//} TCOD_color_t;
struct TCOD_color_t {
        uint8 r,g,b;
};

//typedef void * TCOD_console_t;
alias void* TCOD_console_t;

//TCODLIB_API void TCOD_console_set_default_background(TCOD_console_t  
con,TCOD_color_t col);
void TCOD_console_set_default_background(TCOD_console_t con,TCOD_color_t  
col);

Whenever I use I call this function using TCOD_color_t(255,255,255) it  
seems to set a random other value.
Also, when calling get_default_background (not shown here), I get random  
results back.
I know the library works fine from C, so it has to be somewhere in my  
wrapper.

Does anyone spot any obvious flaws in my wrapping above? Or has any other  
hints on what might have gone wrong?

I've only tested this on linux64.

Thanks.