diff --git a/g10/free-packet.c b/g10/free-packet.c
index 49d54f419..670f2565e 100644
--- a/g10/free-packet.c
+++ b/g10/free-packet.c
@@ -434,11 +434,14 @@ cmp_public_keys( PKT_public_key *a, PKT_public_key *b )
 	return -1;
 
     n = pubkey_get_npkey( b->pubkey_algo );
-    if( !n )
-	return -1; /* can't compare due to unknown algorithm */
-    for(i=0; i < n; i++ ) {
-	if( mpi_cmp( a->pkey[i], b->pkey[i] ) )
-	    return -1;
+    if( !n ) { /* unknown algorithm, rest is in opaque MPI */
+	if( mpi_cmp( a->pkey[0], b->pkey[0] ) )
+	    return -1; /* can't compare due to unknown algorithm */
+    } else {
+	for(i=0; i < n; i++ ) {
+	    if( mpi_cmp( a->pkey[i], b->pkey[i] ) )
+		return -1;
+	}
     }
 
     return 0;