diff --git a/include/psa/crypto_struct.h b/include/psa/crypto_struct.h
index 90a0c2098..6c5639d1c 100644
--- a/include/psa/crypto_struct.h
+++ b/include/psa/crypto_struct.h
@@ -183,7 +183,7 @@ struct psa_aead_operation_s
     size_t ad_length;
 
     uint8_t *body_buffer;
-    uint8_t body_length;
+    size_t body_length;
 
     uint8_t *tag_buffer;