diff --git a/ext/tlib/testsuite.c b/ext/tlib/testsuite.c
index 5d9993cc..fc764ece 100644
--- a/ext/tlib/testsuite.c
+++ b/ext/tlib/testsuite.c
@@ -131,6 +131,11 @@ void tlib_run_tests(int argc, char *argv[])
                 no_abort = 1;
             else if (0 == strcmp("--repeat-forever", a))
                 repeat = ULONG_MAX;
+            else
+            {
+                fprintf(stderr, "tlib_run_tests: unknown option %s\n", a);
+                exit(2);
+            }
         }
         else
             match_any = 0;