diff --git a/eos-s3/btn_counter/README.rst b/eos-s3/btn_counter/README.rst
index da0bef0..595017e 100644
--- a/eos-s3/btn_counter/README.rst
+++ b/eos-s3/btn_counter/README.rst
@@ -7,4 +7,6 @@ counter example, run the following command:
 .. code-block:: bash
    :name: eos-s3-counter
 
+   #FIXME: make sure FPGA_FAM is available and remove env var export
+   export FPGA_FAM=eos-s3
    make -C btn_counter