diff --git a/src/layer.ml b/src/layer.ml
index fd2042c..b18c108 100644
--- a/src/layer.ml
+++ b/src/layer.ml
@@ -85,7 +85,7 @@ let on : type kind. kind Event.sub -> (kind Event.t -> 'b) -> 'c t -> unit =
 (** Geojson layers *)
 
 type geojson_opt =
-  | Point_to_layer of (Jv.t -> Latlng.t -> unit)
+  | Point_to_layer of (Jv.t -> Latlng.t -> [ `Marker ] t)
   | Style of (Jv.t -> unit)
   | On_each_feature of (Jv.t -> [ `Geojson ] t -> unit)
   | Filter of (Jv.t -> bool)
@@ -102,7 +102,9 @@ let geojson_opt_to_string = function
 
 let geojson_opt_to_jv = function
   | Markers_inherit_options b -> Jv.of_bool b
-  | Point_to_layer f -> Jv.repr f
+  | Point_to_layer f ->
+    (* the marker returned by `pointToLayer` is used internally by leaflet so we neet to unwrap it to a Jv.t *)
+    Jv.repr (fun geojsonpoint latlng -> to_jv @@ f geojsonpoint latlng)
   | Style f -> Jv.repr f
   | On_each_feature f ->
     (* we need to wrap the Jv.t *)
diff --git a/src/layer.mli b/src/layer.mli
index 7eaabd2..9c7a7cd 100644
--- a/src/layer.mli
+++ b/src/layer.mli
@@ -52,7 +52,7 @@ val on : 'a Event.sub -> ('a Event.t -> 'b) -> 'c t -> unit
 
 (** type for geojson option, used to create geojson *)
 type geojson_opt =
-  | Point_to_layer of (Jv.t -> Latlng.t -> unit)
+  | Point_to_layer of (Jv.t -> Latlng.t -> [ `Marker ] t)
   | Style of (Jv.t -> unit)
   | On_each_feature of (Jv.t -> [ `Geojson ] t -> unit)
   | Filter of (Jv.t -> bool)