diff --git a/src/program/main.cpp b/src/program/main.cpp
index 31c5d9ff..32c59e47 100644
--- a/src/program/main.cpp
+++ b/src/program/main.cpp
@@ -178,8 +178,8 @@ int main(int argc, char **argv)
                 context.libtas32path = std::filesystem::weakly_canonical(optarg);
                 break;
             case '?':
-                std::cout << "Unknown option character" << std::endl;
-                break;
+                std::cerr << "Unknown option character" << std::endl;
+                return -1;
             case 'h':
                 print_usage();
                 return 0;