diff --git a/snap/snapcraft.yaml b/snap/snapcraft.yaml
index 9be353499..e7e512d07 100644
--- a/snap/snapcraft.yaml
+++ b/snap/snapcraft.yaml
@@ -74,6 +74,10 @@ parts:
     build-packages: [gcc, libffi-dev, libssl-dev, git, libaugeas-dev, python3-dev]
     build-environment:
       - SNAPCRAFT_PYTHON_VENV_ARGS: --system-site-packages
+      # Constraints are passed through the environment variable PIP_CONSTRAINTS instead of using the
+      # parts.[part_name].constraints available in snapcraft.yaml when Python plugin is used, in order
+      # to let these constraints be applied not only on the certbot package build, but also on any
+      # isolated build that pip could trigger to construct transitively dependant wheels.
       - PIP_CONSTRAINT: $SNAPCRAFT_PART_SRC/snap-constraints.txt
     override-pull: |
         snapcraftctl pull