diff --git a/sys/sys/cdefs.h b/sys/sys/cdefs.h
index fcc90b4d8ae..206cc569c55 100644
--- a/sys/sys/cdefs.h
+++ b/sys/sys/cdefs.h
@@ -358,6 +358,17 @@
 #endif
 #endif
 
+/*
+ * noexcept keyword added in C++11.
+ */
+#if defined(__cplusplus) && __cplusplus >= 201103L
+#define __noexcept noexcept
+#define __noexcept_if(__c) noexcept(__c)
+#else
+#define __noexcept
+#define __noexcept_if(__c)
+#endif
+
 /*
  * We use `__restrict' as a way to define the `restrict' type qualifier
  * without disturbing older software that is unaware of C99 keywords.