diff --git a/include/ruby/internal/encoding/encoding.h b/include/ruby/internal/encoding/encoding.h
index db69cc5cc2..9208d27ecf 100644
--- a/include/ruby/internal/encoding/encoding.h
+++ b/include/ruby/internal/encoding/encoding.h
@@ -626,10 +626,10 @@ int rb_enc_codelen(int code, rb_encoding *enc);
 /**
  * Identical to rb_enc_codelen(), except it returns 0 for invalid code points.
  *
- * @param[in]  code       Code point in question.
- * @param[in]  enc        Encoding to convert the code into a byte sequence.
- * @retval     0          `code` is invalid.
- * @return     otherwise  Number of bytes used for `enc` to encode `code`.
+ * @param[in]  c          Code point in question.
+ * @param[in]  enc        Encoding to convert `c` into a byte sequence.
+ * @retval     0          `c` is invalid.
+ * @return     otherwise  Number of bytes needed for `enc` to encode `c`.
  */
 static inline int
 rb_enc_code_to_mbclen(int c, rb_encoding *enc)