diff --git a/CHANGES b/CHANGES
index 82e0333..df5d96c 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,3 +1,7 @@
+0.3.2 ()
+=====
+* Fix compilation with OCaml >= 4.06
+
 0.3.1 (03-08-2015)
 =====
 * Switch to Bytes API.
diff --git a/configure.ac b/configure.ac
index 45e4b21..d807453 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1,6 +1,6 @@
 
 # check for one particular file of the sources 
-AC_INIT([ocaml-lastfm],[0.3.1],[savonet-users@lists.sourceforge.net])
+AC_INIT([ocaml-lastfm],[0.3.2],[savonet-users@lists.sourceforge.net])
 
 VERSION=$PACKAGE_VERSION
 AC_SUBST(VERSION)
diff --git a/m4 b/m4
index 4462789..65ecf99 160000
--- a/m4
+++ b/m4
@@ -1 +1 @@
-Subproject commit 4462789c5a4bb4633ecd993f2240046cb8c46de5
+Subproject commit 65ecf99ebda43e1eb88f278f463370b9738690b0
diff --git a/src/lastfm_generic.ml b/src/lastfm_generic.ml
index 157579c..1a68a3c 100644
--- a/src/lastfm_generic.ml
+++ b/src/lastfm_generic.ml
@@ -57,9 +57,9 @@ let decode64 s =
         | _ -> failwith "decode64: invalid encoding"
     in
     let len = List.length result in
-    let s = String.make len ' ' in
-      ignore (List.fold_left (fun i c -> s.[i] <- c ; i-1) (len-1) result) ;
-      s
+    let s = Bytes.make len ' ' in
+      ignore (List.fold_left (fun i c -> Bytes.set s i c ; i-1) (len-1) result) ;
+      Bytes.to_string s
 
 let parse_url s = 
   let f h p r =
@@ -109,7 +109,7 @@ let to_hex2 =
       let s = Bytes.create 2 in
         Bytes.set s 0 (hex_digits.( (k lsr 4) land 15 )) ;
         Bytes.set s 1 (hex_digits.( k land 15 )) ;
-        s
+        Bytes.to_string s
 
 let url_encode ?(plus=true) s =
   Pcre.substitute