diff --git a/test/test_iomux_signal.c b/test/test_iomux_signal.c
index a3e6406..2d34e05 100644
--- a/test/test_iomux_signal.c
+++ b/test/test_iomux_signal.c
@@ -1,4 +1,5 @@
 #include <check.h>
+#include <errno.h>
 #include <signal.h>
 #include <string.h>
 #include <unistd.h>
@@ -76,8 +77,11 @@ START_TEST (test_iomux_signal_simple)
     ck_assert_int_ne(rc, 0);
 
     raise(SIGUSR1);
+
     iomux_run(mux);
 
+    rc = iomux_unregister_unixsignal(mux, SIGUSR1);
+    ck_assert_int_eq(rc, EINVAL);
 
     iomux_delete(mux);