diff --git a/projects/forest_firefighters/README.md b/projects/forest_firefighters/README.md
index 8c0a81b..217cae0 100644
--- a/projects/forest_firefighters/README.md
+++ b/projects/forest_firefighters/README.md
@@ -3,6 +3,10 @@
 This simulation features a small forest wildfire and a few firefighter robots: a couple of drones and legged robots equipped with cameras.
 Users can run the wildfire simulation and program the behavior of the robots to fight the fire.
 They can also improve the models of the robot and even design new ones.
+
+**Warning**: This project works only with Webots R2021b.
+
+
 ![fire](https://user-images.githubusercontent.com/12995815/131650395-876f5ce5-ecdc-4eb7-83bc-a86f94709e32.png)
 Connect at www.forestfirehub.com for more information about this project.
 
diff --git a/projects/seronet-spawner/README.md b/projects/seronet-spawner/README.md
index d94c347..d627fbe 100644
--- a/projects/seronet-spawner/README.md
+++ b/projects/seronet-spawner/README.md
@@ -6,6 +6,8 @@ This project enables to use a REST API to spawn different kind of boxes, such as
 It comes with two worlds: the first is a demo world (`spawner_demo.wbt`) where the different controllers are already implemented.
 The second, `spawner_seronet.wbt`, is meant to be used with the SeRoNet-Tooling-Collection software, so all the controllers (robot, conveyor belts, etc.) are defined as `<extern>` (except the inner controller of the `ConveyorStation`, `box_creator`, which handles the REST API and is independent).
 
+**Warning**: This project works only with Webots R2021b.
+
 ## Configuration
 
 Both worlds make use of a `ConveyorStation` with 2 `ConveyorStationPlatform`: one is the place where robots deposit boxes to remove, while the other outputs the box requested by the REST API.