strange behavior with record type definition

[Florent <florentflament@aist.enst.fr>]

Hi, I have defined two distinct record's types with a field's name in 
common. But when I try to define a function that uses the first of the 
types, the compiler gives me a type error.
How can I use my first type in a function ??

This is what I did:

# type t0 = { i : int ; s : string };;
type t0 = { i : int; s : string; }
# type t1 = { i : int ; f : float };;
type t1 = { i : int; f : float; }
# let f (x:t0) = match x with {i= a; s= b} -> b;;
Characters 28-40:
  let f (x:t0) = match x with {i= a; s= b} -> b;;
                              ^^^^^^^^^^^^
The record field label s belongs to the type t0
but is here mixed with labels of type t1
#