diff --git a/libc/include/sys/cdefs.h b/libc/include/sys/cdefs.h
index ca81cb6..6bae25c 100644
--- a/libc/include/sys/cdefs.h
+++ b/libc/include/sys/cdefs.h
@@ -510,4 +510,12 @@
 #define __BIONIC_FORTIFY_UNKNOWN_SIZE ((size_t) -1)
 #endif
 
+/* Indicates to client code that <signal.h> now defines 'struct sigcontext'
+ * properly. See comments in <signal.h> */
+#define __BIONIC_HAVE_STRUCT_SIGCONTEXT  1
+
+/* Indicates to client code that <signal.h> now defines 'ucontext_t' */
+/* NOTE: That does not mean that <ucontext.h> is available! */
+#define __BIONIC_HAVE_UCONTEXT_T  1
+
 #endif /* !_SYS_CDEFS_H_ */