diff --git a/alloca.c b/alloca.c
index 7061cec2..12c11229 100644
--- a/alloca.c
+++ b/alloca.c
@@ -25,6 +25,13 @@
 #include <config.h>
 #endif
 
+#ifdef HAVE_STRING_H
+#include <string.h>
+#endif
+#ifdef HAVE_STDLIB_H
+#include <stdlib.h>
+#endif
+
 #ifdef emacs
 #include "blockinput.h"
 #endif