diff --git a/cpdfaddtext.ml b/cpdfaddtext.ml
index 5812b9d..67dab6f 100644
--- a/cpdfaddtext.ml
+++ b/cpdfaddtext.ml
@@ -41,7 +41,7 @@ let width_of_text font text =
   match font with
   | Pdftext.SimpleFont {Pdftext.fontmetrics = Some fontmetrics} ->
        begin try
-         fold_left ( +. ) 0. (map (fun c -> fontmetrics.(int_of_char c)) (explode text))
+         fsum (map (fun c -> fontmetrics.(int_of_char c)) (explode text))
        with
          _ -> 0.
        end
diff --git a/cpdfpng.ml b/cpdfpng.ml
index edc3ade..b9f3702 100644
--- a/cpdfpng.ml
+++ b/cpdfpng.ml
@@ -35,7 +35,7 @@ let read_chunk i =
     (string_of_tag chunktype, chunkdata) 
 
 let concat_bytes ss =
-  let total_length = fold_left ( + ) 0 (map bytes_size ss) in
+  let total_length = sum (map bytes_size ss) in
     let s' = mkbytes total_length in
       let p = ref 0 in
         iter