diff --git a/lib/compiler/Driver.ml b/lib/compiler/Driver.ml
index e0e25b7..16c8406 100644
--- a/lib/compiler/Driver.ml
+++ b/lib/compiler/Driver.ml
@@ -89,6 +89,17 @@ let run_until_done ?(bail = true) a s : State.t =
   in
   go a s
 
+let ensure_loaded ~(forest : State.t) (uri : URI.t) : State.t =
+  if Option.is_some forest.={uri} then forest
+  else
+    let env = State.env forest in
+    let _errors, dirs =
+      Eio_util.paths_of_dirs ~env (State.config forest).trees
+    in
+    match Dir_scanner.find_tree dirs uri with
+    | None -> forest
+    | Some path -> run_until_done ~bail:false (Load_tree path) forest
+
 let batch_run ?(progress = Phases.no_progress) ~env ~(config : Config.t) ~dev ()
     =
   let report action =
diff --git a/lib/language_server/Definitions.ml b/lib/language_server/Definitions.ml
index 302bbdb..8fd714c 100644
--- a/lib/language_server/Definitions.ml
+++ b/lib/language_server/Definitions.ml
@@ -23,8 +23,10 @@ let compute (params : L.DefinitionParams.t) =
   let@ {value = str; _} =
     Option.bind @@ Analysis.addr_at ~position:params.position nodes
   in
-  let uri = URI.named_uri ~base str in
-  let lsp_uri = Option.bind forest.={uri} Tree.lsp_uri in
+  let target_uri = URI.named_uri ~base str in
+  let forest = Driver.ensure_loaded ~forest target_uri in
+  Lsp_state.modify (fun state -> {state with forest});
+  let lsp_uri = Option.bind forest.={target_uri} Tree.lsp_uri in
   let range =
     L.Range.create ~start:{character = 1; line = 0}
       ~end_:{character = 1; line = 0}