diff --git a/library/x509_crt.c b/library/x509_crt.c
index e114c0f..d1d7d73 100644
--- a/library/x509_crt.c
+++ b/library/x509_crt.c
@@ -1652,6 +1652,10 @@
         if( x509_string_cmp( &a->val, &b->val ) != 0 )
             return( -1 );
 
+        /* structure of the list of sets */
+        if( a->next_merged != b->next_merged )
+            return( -1 );
+
         a = a->next;
         b = b->next;
     }