diff --git a/src/base/abc/abcNtk.c b/src/base/abc/abcNtk.c
index d58e9c727..e6a8a5ba5 100644
--- a/src/base/abc/abcNtk.c
+++ b/src/base/abc/abcNtk.c
@@ -1462,9 +1462,10 @@ void Abc_NtkDropOneOutput( Abc_Ntk_t * pNtk, int iOutput )
 {
     Abc_Obj_t * pObj, * pConst0, * pFaninNew;
     pObj = Abc_NtkPo( pNtk, iOutput );
-    if ( Abc_ObjFanin0(pObj) == Abc_AigConst1(pNtk) && !Abc_ObjFaninC0(pObj) )
+    if ( Abc_ObjFanin0(pObj) == Abc_AigConst1(pNtk) )
     {
-        Abc_ObjXorFaninC( pObj, 0 );
+        if ( !Abc_ObjFaninC0(pObj) )
+            Abc_ObjXorFaninC( pObj, 0 );
         return;
     }
     pConst0 = Abc_ObjNot( Abc_AigConst1(pNtk) );