diff --git a/Utils/Util.ml b/Utils/Util.ml
index c19b4fc..e81b8d0 100644
--- a/Utils/Util.ml
+++ b/Utils/Util.ml
@@ -1,4 +1,5 @@
 include Constants
+external erf_float : float -> float = "erf_float_bytecode" "erf_float" [@@unboxed]  [@@noalloc]
 
 let factmax = 150
 
@@ -12,7 +13,10 @@ let rec boys_function ~maxm t =
     begin
       if t = 0. then [| 1. |] else
       let sq_t = sqrt t in
+      (*
       [| (sq_pi_over_two /. sq_t) *.  Gsl.Sf.erf sq_t |]
+      *)
+      [| (sq_pi_over_two /. sq_t) *.  erf_float sq_t |]
     end
   | _ ->
     begin
@@ -87,3 +91,5 @@ let chop f g =
   if (abs_float f) < cutoff then 0.
   else f *. (g ())
 
+
+
diff --git a/Utils/math_functions.c b/Utils/math_functions.c
new file mode 100644
index 0000000..4109aab
--- /dev/null
+++ b/Utils/math_functions.c
@@ -0,0 +1,15 @@
+#include <math.h>
+#include <caml/mlvalues.h>
+#include <caml/alloc.h>
+
+
+CAMLprim value erf_float_bytecode(value x)
+{
+  return copy_double(erf(Double_val(x)));
+}  
+
+CAMLprim double erf_float(double x)
+{
+  return erf(x);
+}
+
diff --git a/_tags b/_tags
index e3819e0..7199fb1 100644
--- a/_tags
+++ b/_tags
@@ -1 +1,3 @@
 true: package(str,gsl,zarith)
+<*.byte>  : linkdep(Utils/math_functions.o)
+<*.native>: linkdep(Utils/math_functions.o)
diff --git a/myocamlbuild.ml b/myocamlbuild.ml
new file mode 100644
index 0000000..321f3e9
--- /dev/null
+++ b/myocamlbuild.ml
@@ -0,0 +1,8 @@
+
+open Ocamlbuild_plugin;;
+
+dispatch (function
+  | After_rules ->
+      pdep ["link"] "linkdep" (fun param -> [param])
+  | _ -> ())
+