diff --git a/tasks/fs0/main.c b/tasks/fs0/main.c
index c34709d..2c720a7 100644
--- a/tasks/fs0/main.c
+++ b/tasks/fs0/main.c
@@ -93,7 +93,7 @@ void handle_fs_requests(void)
 			        (unsigned long)mr[2], (void *)mr[3]);
 		break;
 	default:
-		printf("%s: Unrecognised ipc tag (%d)"
+		printf("%s: Unrecognised ipc tag (%d) "
 		       "received. Ignoring.\n", __TASKNAME__, mr[MR_TAG]);
 	}
 }
diff --git a/tasks/fs0/src/syscalls.c b/tasks/fs0/src/syscalls.c
index c829720..22e0712 100644
--- a/tasks/fs0/src/syscalls.c
+++ b/tasks/fs0/src/syscalls.c
@@ -129,6 +129,7 @@ int sys_open(l4id_t sender, const char *pathname, int flags, unsigned int mode)
 
 	/* Get a new fd */
 	BUG_ON((fd = id_new(task->fdpool)) < 0);
+	retval = fd;
 
 	/* Assign the new fd with the vnode's number */
 	task->fd[fd] = v->vnum;
@@ -339,6 +340,11 @@ int sys_readdir(l4id_t sender, int fd, void *buf, int count)
 		return 0;
 	}
 
+	if (fd < 0 || fd > TASK_OFILES_MAX) {
+	       l4_ipc_return(-EBADF);
+	       return 0;
+	}
+
 	/* Convert fd to vnum. */
 	BUG_ON((vnum = t->fd[fd]) < 0);
 
diff --git a/tasks/test0/src/dirtest.c b/tasks/test0/src/dirtest.c
index 92f74d4..8c7e71c 100644
--- a/tasks/test0/src/dirtest.c
+++ b/tasks/test0/src/dirtest.c
@@ -111,14 +111,14 @@ int lsdir(char *path)
 	memset(dents, 0, sizeof(struct dirent) * DENTS_TOTAL);
 
 	if ((fd = open(path, O_RDONLY)) < 0) {
-		printf("OPEN failed.");
-		return 0;
+		printf("OPEN failed.\n");
+		return -1;
 	} else
 		printf("Got fd: %d for opening %s\n", fd, path);
 
 	if ((bytes = os_readdir(fd, dents, sizeof(struct dirent) * DENTS_TOTAL)) < 0) {
-		perror("GETDENTS\n");
-		return 0;
+		printf("GETDENTS error: %d\n", bytes);
+		return -1;
 	} else {
 		print_dirents(path, dents, bytes);
 	}
@@ -130,9 +130,15 @@ int lsdir(char *path)
 int dirtest(void)
 {
 	printf("\nlsdir current directory:\n");
-	lsdir(".");
+	if (lsdir(".") < 0) {
+		printf("lsdir failed.\n");
+		goto out_err;
+	}
 	printf("\nlsdir root directory:\n");
-	lsdir("/");
+	if (lsdir("/") < 0) {
+		printf("lsdir failed.\n");
+		goto out_err;
+	}
 
 	printf("\nCreating directories: usr, etc, tmp, var, home, opt, bin, boot, lib, dev\n");
 	if (mkdir("/usr", 0) < 0)
@@ -173,5 +179,8 @@ int dirtest(void)
 	printf("\nlsdir /usr/./././bin//\n");
 	lsdir("/usr/./././bin//");
 	return 0;
+
+out_err:
+	return 0;
 }