diff --git a/src/syncterm/telnets.c b/src/syncterm/telnets.c
index f76ae609520f9f77fe51b80450020c2653b84b91..e870008b40b5aa3662a90bf7ffc2a30bbce6d90d 100644
--- a/src/syncterm/telnets.c
+++ b/src/syncterm/telnets.c
@@ -1,8 +1,6 @@
 /* Copyright (C), 2007 by Stephen Hurd */
 
-#include <assert.h>
-
-#if __STDC_NO_ATOMICS__
+#if defined(__STDC_NO_ATOMICS__) && (__STDC_NO_ATOMICS__)
 #error Support for stdatomic.h is required.
 #endif