diff --git a/newlib/libc/include/sys/cdefs.h b/newlib/libc/include/sys/cdefs.h
index 68172ad65..ad2323264 100644
--- a/newlib/libc/include/sys/cdefs.h
+++ b/newlib/libc/include/sys/cdefs.h
@@ -644,6 +644,14 @@
 #define	__DEQUALIFY(type, var)	((type)(__uintptr_t)(const volatile void *)(var))
 #endif
 
+/*
+ * Nullability qualifiers: currently only supported by Clang.
+ */
+#if !(defined(__clang__) && __has_feature(nullability))
+#define	_Nonnull
+#define	_Nullable
+#endif
+
 /*
  * Type Safety Checking
  *