diff --git a/bin/openapi_cli.ml b/bin/openapi_cli.ml
index f3bd547..6959ee7 100644
--- a/bin/openapi_cli.ml
+++ b/bin/openapi_cli.ml
@@ -28,7 +28,11 @@ let with_spec spec_path f =
     if is_yaml_file spec_path spec_content then begin
       Logs.info (fun m -> m "Detected YAML format");
       let codec = Yaml_json.of_json Openapi.Spec.jsont in
-      Yaml.decode_string codec spec_content
+      match Yaml.of_string codec spec_content with
+      | Ok [spec] -> Ok spec
+      | Ok [] -> Error "YAML stream contains no documents"
+      | Ok _ -> Error "YAML stream contains multiple documents; expected one"
+      | Error e -> Error (Yaml.Error.to_string e)
     end else
       Openapi.Spec.of_string spec_content
   in