problem with accents and Catalan characters (for ex. ç) using geocode function (ggmap)

Dear all,

I'm trying to geocode addresses (of Catalonia) with accents and
Catalan characters (as for example "?").  I'm using the "geocode"
function (package ggmap), but I obtain some Google "INVALID_REQUEST"
when the addresses have these characters. For example:

geocode("Carrer Vene?uela, 10, 08019 Barcelona, Spain")

Information from URL :
http://maps.googleapis.com/maps/api/geocode/json?address=Carrer+Vene%E7uela,+10,+08019+Barcelona,+Spain&sensor=false
  lon lat
1  NA  NA
Warning message:
geocode failed with status INVALID_REQUEST, location =
"Carrer+Vene?uela,+10,+08019+Barcelona,+Spain"

geocode("Carrer Mec?nica, 12, 08038 Barcelona, Spain")

Information from URL :
http://maps.googleapis.com/maps/api/geocode/json?address=Carrer+Mec%E0nica,+12,+08038+Barcelona,+Spain&sensor=false
  lon lat
1  NA  NA
Warning message:
geocode failed with status INVALID_REQUEST, location =
"Carrer+Mec?nica,+12,+08038+Barcelona,+Spain"

However, I can find these addresses directly on Google maps.

https://www.google.es/maps/place/Carrer+de+Vene%C3%A7uela,+10,+08019+Barcelona/@41.40873,2.2057253,17z/data=!3m1!4b1!4m2!3m1!1s0x12a4a347b9b9bb8d:0x41b696acd7b26e37

https://www.google.es/maps/place/Carrer+de+la+Mec%C3%A0nica,+12,+08038+Barcelona/@41.3591918,2.1379927,17z/data=!3m1!4b1!4m2!3m1!1s0x12a498a25156dc8b:0xc9ccfd74e54c503f


I think that there is a problem enconding the URL. I hope anyone can
help me! Thank you very much!


Marc