diff --git a/backends/aiger/xaiger.cc b/backends/aiger/xaiger.cc
index c0bd9e921..25e03fa5f 100644
--- a/backends/aiger/xaiger.cc
+++ b/backends/aiger/xaiger.cc
@@ -502,7 +502,7 @@ struct XAigerWriter
 		f << stringf("c\nGenerated by %s\n", yosys_version_str);
 	}
 
-	void write_map(std::ostream &f, bool verbose_map)
+	void write_map(std::ostream &f, bool verbose_map, bool omode)
 	{
 		dict<int, string> input_lines;
 		dict<int, string> init_lines;
@@ -564,6 +564,9 @@ struct XAigerWriter
 		output_lines.sort();
 		for (auto &it : output_lines)
 			f << it.second;
+		if (omode && output_bits.empty()) {
+			f << "output 0 0 __dummy_o__\n";
+		}
 
 		latch_lines.sort();
 		for (auto &it : latch_lines)
@@ -675,7 +678,7 @@ struct XAigerBackend : public Backend {
 			mapf.open(map_filename.c_str(), std::ofstream::trunc);
 			if (mapf.fail())
 				log_error("Can't open file `%s' for writing: %s\n", map_filename.c_str(), strerror(errno));
-			writer.write_map(mapf, verbose_map);
+			writer.write_map(mapf, verbose_map, omode);
 		}
 	}
 } XAigerBackend;