diff --git a/doc/04-schema.md b/doc/04-schema.md
index 05149d331..849e5ee68 100644
--- a/doc/04-schema.md
+++ b/doc/04-schema.md
@@ -160,7 +160,7 @@ The recommended notation for the most common licenses is (alphabetical):
 Optional, but it is highly recommended to supply this. More identifiers are
 listed at the [SPDX Open Source License Registry](https://spdx.org/licenses/).
 
-For closed-source software, you may use `"proprietary"` as the license identifier.
+> **Note:** For closed-source software, you may use `"proprietary"` as the license identifier.
 
 An Example: