diff --git a/tests/test_utils.c b/tests/test_utils.c
index fa9cbc2..e36c672 100644
--- a/tests/test_utils.c
+++ b/tests/test_utils.c
@@ -23,6 +23,12 @@ START_TEST(test_file_get_extension_single) {
   fail_unless(strcmp(extension, "pdf") == 0, NULL);
 } END_TEST
 
+START_TEST(test_file_valid_extension_null) {
+  fail_unless(file_valid_extension(NULL, NULL) == false, NULL);
+  fail_unless(file_valid_extension((void*) 0xDEAD, NULL) == false, NULL);
+  fail_unless(file_valid_extension(NULL, "pdf") == false, NULL);
+} END_TEST
+
 Suite* suite_utils()
 {
   TCase* tcase = NULL;
@@ -40,5 +46,10 @@ Suite* suite_utils()
   tcase_add_test(tcase, test_file_get_extension_single);
   suite_add_tcase(suite, tcase);
 
+  /* file valid extension */
+  tcase = tcase_create("file_valid_extension");
+  tcase_add_test(tcase, test_file_valid_extension_null);
+  suite_add_tcase(suite, tcase);
+
   return suite;
 }