diff --git a/include/polarssl/entropy_poll.h b/include/polarssl/entropy_poll.h
index 9c349da..523a7cd 100644
--- a/include/polarssl/entropy_poll.h
+++ b/include/polarssl/entropy_poll.h
@@ -24,14 +24,14 @@
 #ifndef POLARSSL_ENTROPY_POLL_H
 #define POLARSSL_ENTROPY_POLL_H
 
-#include <string.h>
-
 #if !defined(POLARSSL_CONFIG_FILE)
 #include "config.h"
 #else
 #include POLARSSL_CONFIG_FILE
 #endif
 
+#include <stddef.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif