diff --git a/src/modules/_Roxen/roxen.c b/src/modules/_Roxen/roxen.c
index f75b0f24f5d8ac709d6c7dd28cdda8c66bd537bf..36bcf2f535ce5908829905ba697c299122f799c5 100644
--- a/src/modules/_Roxen/roxen.c
+++ b/src/modules/_Roxen/roxen.c
@@ -377,7 +377,10 @@ static void f_make_http_headers( INT32 args )
 static void f_http_decode_string(INT32 args)
 /*! @decl string http_decode_string(string encoded)
  *!
- *! Decodes an http transport-encoded string.
+ *! Decodes an http transport-encoded string. Knows about %XX and
+ *! %uXXXX syntax. Treats %UXXXX as %uXXXX. It will treat '+' as '+'
+ *! and not ' ', so form decoding needs to replace that in a second
+ *! step.
  */
 {
    int proc;