diff --git a/src/plugins/dive/server_interface.ml b/src/plugins/dive/server_interface.ml
index 0bd290f0608a3cf8d647480f03386158d5eaf152..b428aa3c26a5505067728761cf476339de4d3d6e 100644
--- a/src/plugins/dive/server_interface.ml
+++ b/src/plugins/dive/server_interface.ml
@@ -38,9 +38,16 @@ let get_context =
     match !context with
     | Some c -> c
     | None ->
-      let c = Context.create () in
-      context := Some c;
-      c
+      if Db.Value.is_computed () then
+        let c = Context.create () in
+        context := Some c;
+        c
+      else
+        begin
+          Self.error ~once:true
+            "A prior Eva analysis is required to build the graphs.";
+          Server.Data.failure "Eva analysis not computed"
+        end
 
 
 let global_window = ref {