diff --git a/bob/devtools/data/conda_build_config.yaml b/bob/devtools/data/conda_build_config.yaml
index ed396c482eda2c44817795b741a2f725ff75587f..fbd5485f5a67715877c0e93f2d40af9334559327 100644
--- a/bob/devtools/data/conda_build_config.yaml
+++ b/bob/devtools/data/conda_build_config.yaml
@@ -388,7 +388,7 @@ make:
 matplotlib:
   - 3.4.3
 mkl:
-  - 2020.4
+  - 2020.4  # [x86 or x86_64]
 ncurses:
   - 6.2
 nose: