diff --git a/BaS_gcc/include/xhdi_sd.h b/BaS_gcc/include/xhdi_sd.h
index 0ec5820..dbe42b5 100644
--- a/BaS_gcc/include/xhdi_sd.h
+++ b/BaS_gcc/include/xhdi_sd.h
@@ -53,7 +53,7 @@
 /*
  * FIXME: dangerous TRAP here!
  *
- * all of these functions get compiled with "normal" GCC integers (32 bit). However, since they will be called
+ * all of these functions get compiled into BaS with "normal" GCC integers (32 bit). However, since they will be called
  * from code compiled with -mshort, integers must be declared uint32_t for those compilation units to adhere
  * to "normal" GCC calling conventions.
  *
@@ -67,8 +67,13 @@
 #define UINT16_T	uint16_t
 #endif
 
+/* a riddle: how do you typedef a function pointer to a function that returns its own type? ;) */
+typedef void* (*xhdi_call_fun)(int xhdi_fun, ...);
+
 extern uint32_t xhdi_call(int xhdi_fun, ...);
 
+extern void *xhdi_sd_install(xhdi_call_fun old_vector) __attribute__((__interrupt__));
+
 extern uint32_t xhdi_version(void);	/* XHDI 0 */
 
 extern uint32_t xhdi_inquire_target(UINT16_T major, UINT16_T minor, uint32_t *block_size, uint32_t *flags,
diff --git a/BaS_gcc/sources/xhdi_sd.c b/BaS_gcc/sources/xhdi_sd.c
index 687c867..a13d346 100644
--- a/BaS_gcc/sources/xhdi_sd.c
+++ b/BaS_gcc/sources/xhdi_sd.c
@@ -12,6 +12,14 @@
 
 #define DRIVER_VERSION	0x130
 
+static xhdi_call_fun old_vector = NULL;
+
+__attribute__((__interrupt__)) void *xhdi_sd_install(xhdi_call_fun ov)
+{
+	old_vector = ov;
+	return (void *) xhdi_call;
+}
+
 uint32_t xhdi_version(void)
 {
 	return DRIVER_VERSION;