diff --git a/bob/devtools/data/conda_build_config.yaml b/bob/devtools/data/conda_build_config.yaml
index 270a4ab11972799bff7f0a70b403b97c2817076c..ab7d4fadce5fdb10d06a66d960056309a891af40 100644
--- a/bob/devtools/data/conda_build_config.yaml
+++ b/bob/devtools/data/conda_build_config.yaml
@@ -397,7 +397,7 @@ make:
 matplotlib:
   - 3.4.3
 mkl:
-  - 2020.4
+  - 2020.4  # [x86 or x86_64]
 ncurses:
   - 6.2
 nose: