diff --git a/spec.md b/spec.md
index d4fa3bd..dd224e2 100644
--- a/spec.md
+++ b/spec.md
@@ -212,7 +212,7 @@ progressively greater amount of knowledge."
 **Status:** Required.
 
 **Requirements:**
-- State license initials or name.
+- State license full name or identifier, as listed on the  [SPDX](https://spdx.org/licenses/) license list. For unlicensed repositories, add `UNLICENSED`. For more details, add `SEE LICENSE IN <filename>` and link to the license file. (These requirements were adapted from [npm](https://docs.npmjs.com/files/package.json#license)).
 - State license owner.
 - Must be last section.