diff --git a/modules/conop/src/chemdict_tool.cc b/modules/conop/src/chemdict_tool.cc
index 97d9c45f2cfb3efde54b96b0b3dd81d788242088..36d43ebb094daef9ae8edc7d860a5446dde9a4db 100644
--- a/modules/conop/src/chemdict_tool.cc
+++ b/modules/conop/src/chemdict_tool.cc
@@ -79,7 +79,7 @@ int main(int argc, char const *argv[])
       Logger::Instance().PushVerbosityLevel(0);
     } else {
       PrintUsage();
-      return 0;
+      return 1;
     }
   }
   boost::iostreams::filtering_stream<boost::iostreams::input>  filtered_istream;