--- a/src/scrmode.c	
+++ a/src/scrmode.c	
@@ -94,7 +94,7 @@ #endif /* !no_asm */
 static int screen_w, screen_h;
 
 /* buffers screen image in some modes */
-static BITMAP *__allegro_gl_memory = NULL;
+BITMAP *__allegro_gl_memory = NULL;
 static GFX_VTABLE memory_vtable;    /* vtable for accessing above bitmap */
 static int *dirty_flags = NULL;     /* flags showing dirty lines in bitmap */
 static int dirty_size = 0;          /* size (in bytes) of `dirty_flags' */