diff --git a/doc/configuration.txt b/doc/configuration.txt
index 6f8ffab..31ab590 100644
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -16240,6 +16240,12 @@
   space (' '). Otherwise this will only happen after a question mark indicating
   a query string ('?').
 
+url_enc([<enc_type>])
+  Takes a string provided as input and returns the encoded version as output.
+  The input and the output are of type string. By default the type of encoding
+  is meant for `query` type. There is no other type supported for now but the
+  optional argument is here for future changes.
+
 ungrpc(<field_number>,[<field_type>])
   This extracts the protocol buffers message field in raw mode of an input binary
   sample representation of a gRPC message with <field_number> as field number