diff --git a/include/polarssl/x509_crl.h b/include/polarssl/x509_crl.h
index 3016b87..9f597a8 100644
--- a/include/polarssl/x509_crl.h
+++ b/include/polarssl/x509_crl.h
@@ -75,7 +75,7 @@
     x509_buf raw;           /**< The raw certificate data (DER). */
     x509_buf tbs;           /**< The raw certificate body (DER). The part that is To Be Signed. */
 
-    int version;
+    int version;            /**< CRL version (1=v1, 2=v2) */
     x509_buf sig_oid1;
 
     x509_buf issuer_raw;    /**< The raw issuer data (DER). */