Index: uspace/lib/c/generic/private/futex.h
===================================================================
--- uspace/lib/c/generic/private/futex.h	(revision 45c8eea59f6dced36c60fa4742c6087a34cd81bd)
+++ uspace/lib/c/generic/private/futex.h	(revision f4cb6c5fab0eeda943f0b98226bf10e76be11e76)
@@ -57,6 +57,10 @@
 static inline errno_t futex_destroy(futex_t *futex)
 {
-	if (futex->whandle)
-		return __SYSCALL1(SYS_WAITQ_DESTROY, (sysarg_t) futex->whandle);
+	if (futex->whandle) {
+		errno_t rc;
+		rc = __SYSCALL1(SYS_WAITQ_DESTROY, (sysarg_t) futex->whandle);
+		futex->whandle = CAP_NIL;
+		return rc;
+	}
 	return EOK;
 }