--- a/modules/scicos/src/modelica_compiler/optimization.ml
+++ b/modules/scicos/src/modelica_compiler/optimization.ml
@@ -20,6 +20,7 @@
  *
  *)
 
+open Num
 open SymbolicExpression
 
 
@@ -162,8 +163,7 @@ let num_of_float f =
   let num_of_positive_float f =
     let m, e = frexp f in
     let sm = string_of_float m in
-    let s = String.make 16 '0' in
-    String.blit sm 2 s 0 (String.length sm - 2);
+    let s = String.sub sm 2 (String.length sm - 2) in
     let e' = Num.power_num (Num.Int 2) (Num.num_of_int e) in
     Num.div_num (Num.mult_num (Num.num_of_string s) e') scaling_factor
   in
--- a/modules/scicos/src/modelica_compiler/xMLCodeGeneration.ml
+++ b/modules/scicos/src/modelica_compiler/xMLCodeGeneration.ml
@@ -20,6 +20,7 @@
  *
  *)
 
+open Num
 type 'a tree = Leaf of (string * 'a) | Node of string * 'a tree list
 
 (* function used to hide XML special characters *)