diff --git a/include/polarssl/ecdsa.h b/include/polarssl/ecdsa.h
index cd1987e..d61e82c 100644
--- a/include/polarssl/ecdsa.h
+++ b/include/polarssl/ecdsa.h
@@ -84,7 +84,8 @@
                   const ecp_point *Q, const mpi *r, const mpi *s);
 
 /**
- * \brief           Compute ECDSA signature and write it to buffer
+ * \brief           Compute ECDSA signature and write it to buffer,
+ *                  serialized as defined in RFC 4492 page 20.
  *
  * \param ctx       ECDSA context
  * \param hash      Message hash