diff --git a/libc/include/sys/system_properties.h b/libc/include/sys/system_properties.h
index 2eb00cd..4fdc944 100644
--- a/libc/include/sys/system_properties.h
+++ b/libc/include/sys/system_properties.h
@@ -29,6 +29,10 @@
 #ifndef _INCLUDE_SYS_SYSTEM_PROPERTIES_H
 #define _INCLUDE_SYS_SYSTEM_PROPERTIES_H
 
+#include <sys/cdefs.h>
+
+__BEGIN_DECLS
+
 typedef struct prop_info prop_info;
 
 #define PROP_NAME_MAX   32
@@ -76,4 +80,6 @@
 */ 
 const prop_info *__system_property_find_nth(unsigned n);
 
+__END_DECLS
+
 #endif