diff --git a/include/psa/crypto_struct.h b/include/psa/crypto_struct.h
index 3ff3f93..5ac1875 100644
--- a/include/psa/crypto_struct.h
+++ b/include/psa/crypto_struct.h
@@ -158,7 +158,7 @@
     unsigned int key_set : 1;
     unsigned int iv_required : 1;
     unsigned int iv_set : 1;
-    unsigned int accelerator_set : 1;
+    unsigned int accelerator_set : 1; /* Indicates a driver is used instead of software fallback. */
     uint8_t iv_size;
     uint8_t block_size;
     union