diff --git a/sys/include/tsrb.h b/sys/include/tsrb.h
index 4d9c610dcb..7a2eb4c3a4 100644
--- a/sys/include/tsrb.h
+++ b/sys/include/tsrb.h
@@ -45,14 +45,21 @@ typedef struct tsrb {
 
 /**
  * @brief Static initializer
+ *
+ * @note The size of the buffer (`sizeof(@p BUF)`) must be a power of two.
+ *
+ * @param[in] BUF       Buffer to use by tsrb.
  */
 #define TSRB_INIT(BUF) { (BUF), sizeof (BUF), 0, 0 }
 
 /**
  * @brief        Initialize a tsrb.
+ *
+ * @note The size of the buffer (@p bufsize) must be a power of two.
+ *
  * @param[out]   rb        Datum to initialize.
  * @param[in]    buffer    Buffer to use by tsrb.
- * @param[in]    bufsize   `sizeof (buffer)`, must be power of 2.
+ * @param[in]    bufsize   Size of @p buffer.
  */
 static inline void tsrb_init(tsrb_t *rb, uint8_t *buffer, unsigned bufsize)
 {