diff --git a/src/coding/gsm0503_coding.c b/src/coding/gsm0503_coding.c
index f2b0180..07c8c98 100644
--- a/src/coding/gsm0503_coding.c
+++ b/src/coding/gsm0503_coding.c
@@ -606,7 +606,7 @@
 
 /*! convenience wrapper for encoding to coded bits
  *  \param[out] cB caller-allocated buffer for 456 coded bits as per TS 05.03 4.1.3
- *  \param[out] l2_data to-be-encoded L2 Frame
+ *  \param[in] l2_data to-be-encoded L2 Frame
  *  \returns 0 */
 static int _xcch_encode_cB(ubit_t *cB, const uint8_t *l2_data)
 {