diff --git a/include/polarssl/x509write.h b/include/polarssl/x509write.h
index 9d43efb..ea1ba7a 100644
--- a/include/polarssl/x509write.h
+++ b/include/polarssl/x509write.h
@@ -27,6 +27,8 @@
 #ifndef POLARSSL_X509_WRITE_H
 #define POLARSSL_X509_WRITE_H
 
+#if defined(POLARSSL_X509_WRITE_C)
+
 #include "rsa.h"
 
 typedef struct _x509_req_name
@@ -43,4 +45,6 @@
 int x509_write_cert_req( unsigned char *buf, size_t size, rsa_context *rsa,
                          x509_req_name *req_name, md_type_t md_alg );
 
+#endif /* POLARSSL_X509_WRITE_C */
+
 #endif /* POLARSSL_X509_WRITE_H */