diff --git a/pico/pico.h b/pico/pico.h
index a1aa96ee..d22babd5 100644
--- a/pico/pico.h
+++ b/pico/pico.h
@@ -172,6 +172,7 @@ typedef enum
 void PicoDrawSetOutFormat(pdso_t which, int use_32x_line_mode);
 void PicoDrawSetOutBuf(void *dest, int increment);
 void PicoDrawSetCallbacks(int (*begin)(unsigned int num), int (*end)(unsigned int num));
+extern unsigned char *HighCol;
 // utility
 #ifdef _ASM_DRAW_C
 void vidConvCpyRGB565(void *to, void *from, int pixels);