diff --git a/include/polarssl/x509write.h b/include/polarssl/x509write.h
index acff33d..aa4d053 100644
--- a/include/polarssl/x509write.h
+++ b/include/polarssl/x509write.h
@@ -29,7 +29,7 @@
 
 #include "config.h"
 
-#include "rsa.h"
+#include "x509.h"
 
 /**
  * \addtogroup x509_module
@@ -80,6 +80,7 @@
     rsa_context *rsa;
     x509_req_name *subject;
     md_type_t md_alg;
+    unsigned char key_usage;
 }
 x509_csr;
 
@@ -125,6 +126,15 @@
 void x509write_csr_set_md_alg( x509_csr *ctx, md_type_t md_alg );
 
 /**
+ * \brief           Set the Key Usage Extension flags
+ *                  (e.g. KU_DIGITAL_SIGNATURE | KU_KEY_CERT_SIGN)
+ *
+ * \param ctx       CSR context to use
+ * \param key_usage key usage bitstring to set
+ */
+void x509write_csr_set_key_usage( x509_csr *ctx, unsigned char key_usage );
+
+/**
  * \brief           Free the contents of a CSR context
  *
  * \param ctx       CSR context to free