diff --git a/src/extract.c b/src/extract.c
index f74edc7..b98d6c4 100644
--- a/src/extract.c
+++ b/src/extract.c
@@ -437,10 +437,17 @@ int main (int argc, char *argv[])
 			error->message); /* howto translate? */
 		fprintf(stderr, g_option_context_get_help(context,
 							  FALSE, NULL));
+		return 1;
 	}
 
-	if (g_access(driver_filename, R_OK)) {
+	if (driver_filename == NULL) { 
+	  fprintf(stderr, _("Option -a is mandatory. See --help.\n"));
+	  return 1;
+	}
+
+	if (g_access(driver_filename, R_OK | F_OK)) {
 		g_error(_("Unable to read driver %s."), driver_filename);
+		return 1;
 	}
 
 	pathname = g_build_filename(firmware_dir, firmware_filename, NULL);
@@ -450,7 +457,7 @@ int main (int argc, char *argv[])
 	 * iSight and thus possibly damaging it. */
 	digest = get_sha1sum(driver_filename);
 	if (!digest) {
-		return -1;
+		return 1;
 	}
 
 	sha1sum = sha1sum_string(digest);