diff --git a/os/busfault.h b/os/busfault.h
index 0cc5a6d802..21957b2fef 100644
--- a/os/busfault.h
+++ b/os/busfault.h
@@ -29,12 +29,12 @@
 
 #include "misc.h"                         /* for TRUE/FALSE */
 
+typedef void (*busfault_notify_ptr) (void *context);
+
 #ifdef HAVE_SIGACTION
 
 #include <sys/types.h>
 
-typedef void (*busfault_notify_ptr) (void *context);
-
 struct busfault *
 busfault_register_mmap(void *addr, size_t size, busfault_notify_ptr notify, void *context);
 
@@ -49,6 +49,24 @@ busfault_init(void);
 
 #else
 
+struct busfault;
+
+static inline struct busfault *
+busfault_register_mmap(void *addr, size_t size, busfault_notify_ptr notify, void *context)
+{
+    (void) addr;
+    (void) size;
+    (void) notify;
+    (void) context;
+    return NULL;
+}
+
+static inline void
+busfault_unregister(struct busfault *busfault)
+{
+    (void) busfault;
+}
+
 static inline void busfault_check(void) {}
 static inline Bool busfault_init(void) { return FALSE; }