diff --git a/README.md b/README.md
index 48be6610e5ff6ffa627a821e5c4044dcb71dca91..65dcaff386aae61b92bb5e316f28ea517f69825a 100644
--- a/README.md
+++ b/README.md
@@ -56,6 +56,7 @@ In order to remove an old conda distribution (like miniconda/anaconda) you need
 
 - Make sure that `conda config --show-sources` / `conda config --show channels` does not show the `defaults` channel.
 - If you find the `defaults` channel, remove it by executing `conda config --remove channels defaults`. If desired you can add `conda-forge` like so: `conda config --add channels conda-forge`
+- Just to be sure, one can explicit forbid the usage of the channels: `conda config --append denylist_channels defaults`, `conda config --append denylist_channels main`, `conda config --append denylist_channels r`
 - Make sure that `override_channels_enabled` is enabled: `conda config --show override_channels_enabled` should show `True`.
 If needed set it with `conda config --set override_channels_enabled True`.
 - It might be also a good idea to add [`nodefaults`](https://docs.conda.io/projects/conda/en/4.6.1/user-guide/tasks/manage-environments.html#creating-an-environment-file-manually) to the channel list, even if it's documented as equivalent to `override_channels_enabled`