diff --git a/include/polarssl/cipher.h b/include/polarssl/cipher.h
index 23b0f3d..27dc7b9 100644
--- a/include/polarssl/cipher.h
+++ b/include/polarssl/cipher.h
@@ -296,7 +296,7 @@
  *
  * \returns             0 on success, 1 if parameter verification fails.
  */
-int cipher_setkey( cipher_context_t *ctx, const unsigned char *key, int key_len,
+int cipher_setkey( cipher_context_t *ctx, const unsigned char *key, int key_length,
         const operation_t operation );
 
 /**