diff --git a/include/polarssl/cipher.h b/include/polarssl/cipher.h
index 999d24b..e291ef6 100644
--- a/include/polarssl/cipher.h
+++ b/include/polarssl/cipher.h
@@ -33,6 +33,8 @@
 #include POLARSSL_CONFIG_FILE
 #endif
 
+#include <stddef.h>
+
 #if defined(POLARSSL_GCM_C) || defined(POLARSSL_CCM_C)
 #define POLARSSL_CIPHER_MODE_AEAD
 #endif
@@ -41,8 +43,6 @@
 #define POLARSSL_CIPHER_MODE_WITH_PADDING
 #endif
 
-#include <string.h>
-
 #if defined(_MSC_VER) && !defined(inline)
 #define inline _inline
 #else