diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..e35d885
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+_build
diff --git a/builder-web.opam b/builder-web.opam
index c2264e9..36e0b9a 100644
--- a/builder-web.opam
+++ b/builder-web.opam
@@ -43,7 +43,7 @@ depends: [
   "logs"
   "cmdliner"
   "uri"
-  "fmt"
+  "fmt" {>= "0.8.7"}
   "omd"
 ]
 
diff --git a/lib/builder_web.ml b/lib/builder_web.ml
index 142917a..05c9ddf 100644
--- a/lib/builder_web.ml
+++ b/lib/builder_web.ml
@@ -126,7 +126,7 @@ let add_routes datadir =
     >>= Model.not_found
     |> if_error "Error getting job" >>= fun build ->
     Dream.redirect req
-      (Fmt.strf "/job/%s/build/%a/%s" job_name Uuidm.pp build path)
+      (Fmt.str "/job/%s/build/%a/%s" job_name Uuidm.pp build path)
     |> Lwt_result.ok
   in
 
@@ -144,7 +144,7 @@ let add_routes datadir =
       Dream.sql req (Model.build_artifact_by_id main_binary)
       |> if_error "Error getting main binary" >>= fun main_binary ->
       Dream.redirect req
-        (Fmt.strf "/job/%s/build/%a/f/%a" job_name Uuidm.pp uuid
+        (Fmt.str "/job/%s/build/%a/f/%a" job_name Uuidm.pp uuid
           Fpath.pp main_binary.Builder_db.filepath)
       |> Lwt_result.ok
   in
@@ -234,7 +234,7 @@ let add_routes datadir =
     | true ->
       Log.warn (fun m -> m "Build with same uuid exists: %a" pp_exec exec);
       Dream.respond ~status:`Conflict
-        (Fmt.strf "Build with same uuid exists: %a\n" Uuidm.pp uuid)
+        (Fmt.str "Build with same uuid exists: %a\n" Uuidm.pp uuid)
       |> Lwt_result.ok
     | false ->
       let datadir = Dream.global datadir_global req in
@@ -256,7 +256,7 @@ let add_routes datadir =
     Dream.sql req (Model.build_hash hash) >>= Model.not_found
     |> if_error "Internal server error" >>= fun (job_name, build) ->
     Dream.redirect req
-      (Fmt.strf "/job/%s/build/%a/" job_name Uuidm.pp build.Builder_db.Build.uuid)
+      (Fmt.str "/job/%s/build/%a/" job_name Uuidm.pp build.Builder_db.Build.uuid)
     |> Lwt_result.ok
   in
 
@@ -313,7 +313,7 @@ let add_routes datadir =
     | true ->
       Log.warn (fun m -> m "Build %S with same uuid exists: %a" job Uuidm.pp uuid);
       Dream.respond ~status:`Conflict
-        (Fmt.strf "Build with same uuid exists: %a\n" Uuidm.pp uuid)
+        (Fmt.str "Build with same uuid exists: %a\n" Uuidm.pp uuid)
       |> Lwt_result.ok
     | false ->
       let datadir = Dream.global datadir_global req in
diff --git a/lib/views.ml b/lib/views.ml
index 522d00c..4c6a880 100644
--- a/lib/views.ml
+++ b/lib/views.ml
@@ -2,8 +2,8 @@ open Tyxml.Html
 
 let pp_ptime = Ptime.pp_human ()
 
-let txtf fmt = Fmt.kstrf txt fmt
-let a_titlef fmt = Fmt.kstrf a_title fmt
+let txtf fmt = Fmt.kstr txt fmt
+let a_titlef fmt = Fmt.kstr a_title fmt
 
 let check_icon result =
   match result with
@@ -81,7 +81,7 @@ let toggleable ?(hidden=true) id description content =
 
 let artifact ?(basename=false) job_name build { Builder_db.filepath; localpath = _; sha256; size } =
   [
-    a ~a:[a_href (Fmt.strf "/job/%s/build/%a/f/%a"
+    a ~a:[a_href (Fmt.str "/job/%s/build/%a/f/%a"
                     job_name
                     Uuidm.pp build.Builder_db.Build.uuid
                     Fpath.pp filepath)]
@@ -136,7 +136,7 @@ let builder section_job_map =
                    br ();
                    txt (Option.value ~default:"" synopsis);
                    br ();
-                   a ~a:[a_href (Fmt.strf "job/%s/build/%a/" job_name Uuidm.pp
+                   a ~a:[a_href (Fmt.str "job/%s/build/%a/" job_name Uuidm.pp
                                    latest_build.Builder_db.Build.uuid)]
                      [txtf "%a" (Ptime.pp_human ()) latest_build.Builder_db.Build.start];
                    txt " ";
@@ -199,7 +199,7 @@ let job_build
   =
   let delta = Ptime.diff finish start in
   let successful_build = match result with Builder.Exited 0 -> true | _ -> false in
-  layout ~title:(Fmt.strf "Job %s %a" name pp_ptime start)
+  layout ~title:(Fmt.str "Job %s %a" name pp_ptime start)
     ((h1 [txtf "Job %s" name] ::
       (match readme with
        | None -> []
@@ -345,20 +345,20 @@ let compare_opam job_left job_right
     (added_env, removed_env, changed_env)
     (added_pkgs, removed_pkgs, changed_pkgs)
     (same, opam_diff, version_diff, left, right) =
-  layout ~title:(Fmt.strf "Comparing opam switches between builds %a and %a"
+  layout ~title:(Fmt.str "Comparing opam switches between builds %a and %a"
                    Uuidm.pp build_left.uuid Uuidm.pp build_right.uuid)
     ([
       h1 [txt "Comparing opam switches"];
       h2 [
         txt "Builds ";
         a ~a:[a_href
-               (Fmt.strf "/job/%s/build/%a/"
+               (Fmt.str "/job/%s/build/%a/"
                   job_left
                   Uuidm.pp build_left.uuid)]
           [txtf "%a" pp_ptime build_left.start];
         txt " and ";
         a ~a:[a_href
-               (Fmt.strf "/job/%s/build/%a/"
+               (Fmt.str "/job/%s/build/%a/"
                   job_right
                   Uuidm.pp build_right.uuid)]
           [txtf "%a" pp_ptime build_right.start];