nghttpx: Backend API call allows non-numeric host with dns parameter

doc/nghttpx.1.rst

@@ -1767,10 +1767,10 @@ The replacement is done instantly without breaking existing
 connections or requests.  It also avoids any process creation as is
 the case with hot swapping with signals.
 
-The one limitation is that only numeric IP address is allowd in
-:option:`backend <--backend>` in request body while non numeric
-hostname is allowed in command-line or configuration file is read
-using :option:`--conf`.
+The one limitation is that only numeric IP address is allowed in
+:option:`backend <--backend>` in request body unless "dns" parameter
+is missing while non numeric hostname is allowed in command-line or
+configuration file is read using :option:`--conf`.
 
 SEE ALSO
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