diff --git a/src/aig/aig/aigOper.c b/src/aig/aig/aigOper.c
index d6f02a6e0..63f8717ce 100644
--- a/src/aig/aig/aigOper.c
+++ b/src/aig/aig/aigOper.c
@@ -118,6 +118,8 @@ Aig_Obj_t * Aig_And( Aig_Man_t * p, Aig_Obj_t * p0, Aig_Obj_t * p1 )
     if ( p->fAddStrash && (Aig_ObjIsNode(Aig_Regular(p0)) || Aig_ObjIsNode(Aig_Regular(p1))) )
     { // http://fmv.jku.at/papers/BrummayerBiere-MEMICS06.pdf
         Aig_Obj_t * pFanA, * pFanB, * pFanC, * pFanD;
+        if ( Aig_Regular(p0)->Id > Aig_Regular(p1)->Id )
+            ABC_SWAP( Aig_Obj_t *, p0, p1 );
         pFanA = Aig_ObjChild0(Aig_Regular(p0));
         pFanB = Aig_ObjChild1(Aig_Regular(p0));
         pFanC = Aig_ObjChild0(Aig_Regular(p1));