diff --git a/include/polarssl/pem.h b/include/polarssl/pem.h
index c0775d0..9ccdbef 100644
--- a/include/polarssl/pem.h
+++ b/include/polarssl/pem.h
@@ -24,7 +24,7 @@
 #ifndef POLARSSL_PEM_H
 #define POLARSSL_PEM_H
 
-#include <string.h>
+#include <stddef.h>
 
 /**
  * \name PEM Error codes