diff --git a/libc/include/alloca.h b/libc/include/alloca.h
index 0c50fc3..0508d31 100644
--- a/libc/include/alloca.h
+++ b/libc/include/alloca.h
@@ -25,9 +25,12 @@
  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  */
+
 #ifndef _ALLOCA_H
 #define _ALLOCA_H
 
+#include <sys/cdefs.h>
+
 #define alloca(size)   __builtin_alloca(size)
 
 #endif /* _ALLOCA_H */