diff --git a/docs/library/ubinascii.rst b/docs/library/ubinascii.rst
index 192d34514b..721b80508e 100644
--- a/docs/library/ubinascii.rst
+++ b/docs/library/ubinascii.rst
@@ -14,13 +14,11 @@ Functions
 
 .. function:: hexlify(data, [sep])
 
-   Convert binary data to hexadecimal representation. Returns bytes string.
+   Convert the bytes in the *data* object to a hexadecimal representation.
+   Returns a bytes object.
 
-   .. admonition:: Difference to CPython
-      :class: attention
-
-      If additional argument, *sep* is supplied, it is used as a separator
-      between hexadecimal values.
+   If the additional argument *sep* is supplied it is used as a separator
+   between hexadecimal values.
 
 .. function:: unhexlify(data)
 
diff --git a/extmod/modubinascii.c b/extmod/modubinascii.c
index 1d4c72b24b..9e4f86fbd2 100644
--- a/extmod/modubinascii.c
+++ b/extmod/modubinascii.c
@@ -34,8 +34,8 @@
 #if MICROPY_PY_UBINASCII
 
 STATIC mp_obj_t mod_binascii_hexlify(size_t n_args, const mp_obj_t *args) {
-    // Second argument is for an extension to allow a separator to be used
-    // between values.
+    // First argument is the data to convert.
+    // Second argument is an optional separator to be used between values.
     const char *sep = NULL;
     mp_buffer_info_t bufinfo;
     mp_get_buffer_raise(args[0], &bufinfo, MP_BUFFER_READ);