diff --git a/docs/architecture/psa-migration/psa-limitations.md b/docs/architecture/psa-migration/psa-limitations.md
index 724e29b69c..f5b5700ab8 100644
--- a/docs/architecture/psa-migration/psa-limitations.md
+++ b/docs/architecture/psa-migration/psa-limitations.md
@@ -317,7 +317,7 @@ strong security arguments, so it's unclear whether it would be accepted.
 HKDF: Expand not exposed on its own (TLS 1.3)
 ---------------------------------------------
 
-The HKDF function uses and Extract-then-Expand approach, that is:
+The HKDF function uses an Extract-then-Expand approach, that is:
 
         HKDF(x, ...) = HKDF-Expand(HKDF-Extract(x, ...), ...)