diff --git a/src/lib/uTop_styles.ml b/src/lib/uTop_styles.ml
index 6a12f70..44f045c 100644
--- a/src/lib/uTop_styles.ml
+++ b/src/lib/uTop_styles.ml
@@ -80,7 +80,7 @@ let load () =
       styles.style_foreground <- LTerm_resources.get_color "foreground" res;
       styles.style_background <- LTerm_resources.get_color "background" res;
       styles.style_cursor <- LTerm_resources.get_color "cursor" res;
-      (match String.lowercase (LTerm_resources.get "profile" res) with
+      (match String.lowercase_ascii (LTerm_resources.get "profile" res) with
          | "light" -> UTop.set_profile UTop.Light
          | "dark" -> UTop.set_profile UTop.Dark
          | "" -> ()
diff --git a/utop.opam b/utop.opam
index 464452c..f33f3cb 100644
--- a/utop.opam
+++ b/utop.opam
@@ -22,4 +22,4 @@ depends: [
   "jbuilder"     {build & >= "1.0+beta9"}
 ]
 build-test: [["jbuilder" "runtest" "-p" name "-j" jobs]]
-available: [ocaml-version >= "4.02.3"]
+available: [ocaml-version >= "4.03.0"]