diff --git a/src/fop.rs b/src/fop.rs
index b6da510..261aba5 100644
--- a/src/fop.rs
+++ b/src/fop.rs
@@ -61,6 +61,8 @@ fn main() -> ExitCode {
 		}
 	}
 
+	if argv.len() == 1 { return ExitCode::from(usage(&argv[0])); }
+
 	while let Some(opt) = argv.getopt("d:") {
 		match opt.opt() {
 			Ok("d") => {
diff --git a/tests/bonsai/fop.mk b/tests/bonsai/fop.mk
index b538031..230e1c1 100755
--- a/tests/bonsai/fop.mk
+++ b/tests/bonsai/fop.mk
@@ -24,6 +24,7 @@ fop_fail: $(BIN)/fop
 	! printf 'test\n' | $(BIN)/fop 1 cat
 	! printf 'test\n' | $(BIN)/fop 'test' cat
 	! printf 'test\n' | $(BIN)/fop -d'test' cat
+	! $(BIN)/fop
 
 .PHONY: fop_functionality
 fop_functionality: $(BIN)/fop