diff --git a/sw/airborne/lisa/plug_sys.c b/sw/airborne/lisa/plug_sys.c
index 736cf3268d..170393a124 100644
--- a/sw/airborne/lisa/plug_sys.c
+++ b/sw/airborne/lisa/plug_sys.c
@@ -15,10 +15,10 @@ extern int                    _close(int);
 extern ssize_t                _read(int, void *, size_t);
 
 off_t                  _lseek(int a, off_t b, int c) { return b;}
-void                   abort(void) {}
+void                   abort(void) {while(1){};}
 pid_t                  getpid(void) { return 0;}
-int                    kill(pid_t a, int b) {}
-void *                 _sbrk(int a) {}
+int                    kill(pid_t a, int b) {return 0;}
+void *                 _sbrk(int a) {return 0;}
 ssize_t                _write(int a, const void *b, size_t c) {return 0; }
 int                    _close(int a) { return 0;}
 ssize_t                _read(int a, void *b, size_t c) {return 0;}