diff --git a/include/stdlib.h b/include/stdlib.h
index 9c8a1182..ed512f43 100644
--- a/include/stdlib.h
+++ b/include/stdlib.h
@@ -128,7 +128,7 @@ void lcong48 (unsigned short [7]);
 #endif
 
 #if defined(_GNU_SOURCE)
-void *alloca(size_t);
+#include <alloca.h>
 char *mktemp (char *);
 void *valloc (size_t);
 void *memalign(size_t, size_t);