diff --git a/backends/aiger/xaiger.cc b/backends/aiger/xaiger.cc
index a4ef89931..bad9322bb 100644
--- a/backends/aiger/xaiger.cc
+++ b/backends/aiger/xaiger.cc
@@ -229,7 +229,7 @@ struct XAigerWriter
 					}
 					if (is_output) {
 						SigBit O = sigmap(b);
-						if (!input_bits.count(O) && !output_bits.count(O))
+						if (!input_bits.count(O))
 							ci_bits.insert(O);
 					}
 				}