diff --git a/include/polarssl/camellia.h b/include/polarssl/camellia.h
index 1b144e7..9bf5e91 100644
--- a/include/polarssl/camellia.h
+++ b/include/polarssl/camellia.h
@@ -72,6 +72,8 @@
 
 /**
  * \brief          CAMELLIA-CBC buffer encryption/decryption
+ *                 Length should be a multiple of the block
+ *                 size (16 bytes)
  *
  * \param ctx      CAMELLIA context
  * \param mode     CAMELLIA_ENCRYPT or CAMELLIA_DECRYPT