Assigned error codes to the error defines
diff --git a/include/polarssl/x509write.h b/include/polarssl/x509write.h
index c95172f..2933b2f 100644
--- a/include/polarssl/x509write.h
+++ b/include/polarssl/x509write.h
@@ -31,9 +31,10 @@
#include "rsa.h"
-#define POLARSSL_ERR_X509_WRITE_UNKNOWN_OID -1
-#define POLARSSL_ERR_X509_WRITE_BAD_INPUT_DATA -1
-#define POLARSSL_ERR_X509_WRITE_MALLOC_FAILED -1
+#define POLARSSL_ERR_X509WRITE_UNKNOWN_OID -0x5F80 /**< Requested OID is unknown. */
+#define POLARSSL_ERR_X509WRITE_BAD_INPUT_DATA -0x5F00 /**< Failed to allocate memory. */
+#define POLARSSL_ERR_X509WRITE_MALLOC_FAILED -0x5E80 /**< Failed to allocate memory. */
+
#ifdef __cplusplus
extern "C" {