diff --git a/tools/compute-hops/main.cc b/tools/compute-hops/main.cc
index 2f3979de..0c1134a7 100644
--- a/tools/compute-hops/main.cc
+++ b/tools/compute-hops/main.cc
@@ -40,7 +40,7 @@ int main(int argc, char *argv[])
 	// Manually fill the command line option parser
 	CommandLine &cmd = CommandLine::Inst();
 
-	cmd.addOption("", "", Arg::None, "USAGE: compute-hops [options]");
+	CommandLine::option_handle UNKNOWN = cmd.addOption("", "", Arg::None, "USAGE: compute-hops [options]");
 	CommandLine::option_handle HELP = cmd.addOption("h", "help", Arg::None, "-h,--help \tPrint usage and exit");
 
 	CommandLine::option_handle ALGORITHM =
@@ -99,7 +99,13 @@ int main(int argc, char *argv[])
 		return 1;
 	}
 
-	if (cmd[HELP]) {
+	if (cmd[HELP] || cmd[UNKNOWN] || cmd.parser()->nonOptionsCount() > 0) {
+		for (option::Option* opt = cmd[UNKNOWN]; opt; opt = opt->next()) {
+			std::cerr << "Unknown option: " << opt->name << "\n";
+		}
+		for (int i = 0; i < cmd.parser()->nonOptionsCount(); ++i) {
+			std::cerr << "Unknown non-option: " << cmd.parser()->nonOption(i) << "\n";
+		}
 		cmd.printUsage();
 		if (cmd[HELP]) {
 			exit(0);
diff --git a/tools/convert-trace/main.cc b/tools/convert-trace/main.cc
index 359d3806..45330ba4 100644
--- a/tools/convert-trace/main.cc
+++ b/tools/convert-trace/main.cc
@@ -17,7 +17,8 @@ static Logger LOG("convert-trace", true);
 
 int main(int argc, char *argv[]) {
 	CommandLine &cmd = CommandLine::Inst();
-	cmd.addOption("", "", Arg::None, "usage: convert-trace -f dump|gem5 -t tracefile.tc");
+	CommandLine::option_handle UNKNOWN =
+		cmd.addOption("", "", Arg::None, "usage: convert-trace -f dump|gem5 -t tracefile.tc");
 	CommandLine::option_handle HELP =
 		cmd.addOption("h", "help", Arg::None, "-h/--help \tPrint usage and exit");
 	CommandLine::option_handle FORMAT =
@@ -28,11 +29,17 @@ int main(int argc, char *argv[]) {
 		cmd.add_args(argv[i]);
 	}
 	if (!cmd.parse()) {
-		LOG << "Error parsing arguments." << endl;
+		std::cerr << "Error parsing arguments." << endl;
 		return 1;
 	}
 
-	if (cmd[HELP] || !cmd[OUTFILE] || !cmd[FORMAT] || cmd.parser()->nonOptionsCount() != 0) {
+	if (cmd[HELP] || !cmd[OUTFILE] || !cmd[FORMAT] || cmd[UNKNOWN] || cmd.parser()->nonOptionsCount() != 0) {
+		for (option::Option* opt = cmd[UNKNOWN]; opt; opt = opt->next()) {
+			std::cerr << "Unknown option: " << opt->name << "\n";
+		}
+		for (int i = 0; i < cmd.parser()->nonOptionsCount(); ++i) {
+			std::cerr << "Unknown non-option: " << cmd.parser()->nonOption(i) << "\n";
+		}
 		cmd.printUsage();
 		if (cmd[HELP]) {
 			exit(0);
diff --git a/tools/dump-hops/DumpHops.cc b/tools/dump-hops/DumpHops.cc
index dd3c88c0..e64695bc 100644
--- a/tools/dump-hops/DumpHops.cc
+++ b/tools/dump-hops/DumpHops.cc
@@ -49,7 +49,8 @@ int main(int argc, char *argv[])
 	InjectionPointMessage ev;
 
 	CommandLine &cmd = CommandLine::Inst();
-	cmd.addOption("", "", Arg::None, "usage: dump-hops [options] hopfile.hp");
+	CommandLine::option_handle UNKNOWN =
+		cmd.addOption("", "", Arg::None, "usage: dump-hops [options] hopfile.hp");
 	CommandLine::option_handle HELP =
 		cmd.addOption("h", "help", Arg::None, "-h/--help \tPrint usage and exit");
 //	CommandLine::option_handle STATS =
@@ -64,7 +65,13 @@ int main(int argc, char *argv[])
 		return 1;
 	}
 
-	if (cmd[HELP] || cmd.parser()->nonOptionsCount() != 1) {
+	if (cmd[HELP] || cmd[UNKNOWN] || cmd.parser()->nonOptionsCount() != 1) {
+		for (option::Option* opt = cmd[UNKNOWN]; opt; opt = opt->next()) {
+			std::cerr << "Unknown option: " << opt->name << "\n";
+		}
+		for (int i = 1; i < cmd.parser()->nonOptionsCount(); ++i) {
+			std::cerr << "Unknown non-option: " << cmd.parser()->nonOption(i) << "\n";
+		}
 		cmd.printUsage();
 		if (cmd[HELP]) {
 			exit(0);
diff --git a/tools/dump-trace/DumpTrace.cc b/tools/dump-trace/DumpTrace.cc
index 0015cec2..d86ee5e9 100644
--- a/tools/dump-trace/DumpTrace.cc
+++ b/tools/dump-trace/DumpTrace.cc
@@ -49,7 +49,8 @@ int main(int argc, char *argv[])
 	Trace_Event ev;
 
 	CommandLine &cmd = CommandLine::Inst();
-	cmd.addOption("", "", Arg::None, "usage: dump-trace [options] tracefile.tc");
+	CommandLine::option_handle UNKNOWN =
+		cmd.addOption("", "", Arg::None, "usage: dump-trace [options] tracefile.tc");
 	CommandLine::option_handle HELP =
 		cmd.addOption("h", "help", Arg::None, "-h/--help \tPrint usage and exit");
 	CommandLine::option_handle STATS =
@@ -67,7 +68,13 @@ int main(int argc, char *argv[])
 		return 1;
 	}
 
-	if (cmd[HELP] || cmd.parser()->nonOptionsCount() != 1) {
+	if (cmd[HELP] || cmd[UNKNOWN] || cmd.parser()->nonOptionsCount() != 1) {
+		for (option::Option* opt = cmd[UNKNOWN]; opt; opt = opt->next()) {
+			std::cerr << "Unknown option: " << opt->name << "\n";
+		}
+		for (int i = 1; i < cmd.parser()->nonOptionsCount(); ++i) {
+			std::cerr << "Unknown non-option: " << cmd.parser()->nonOption(i) << "\n";
+		}
 		cmd.printUsage();
 		if (cmd[HELP]) {
 			exit(0);
diff --git a/tools/import-trace/main.cc b/tools/import-trace/main.cc
index 9259b612..d039b870 100644
--- a/tools/import-trace/main.cc
+++ b/tools/import-trace/main.cc
@@ -85,7 +85,8 @@ int main(int argc, char *argv[]) {
 	for (int i = 1; i < argc; ++i)
 		cmd.add_args(argv[i]);
 
-	cmd.addOption("", "", Arg::None, "USAGE: import-trace [options]");
+	CommandLine::option_handle UNKNOWN =
+		cmd.addOption("", "", Arg::None, "USAGE: import-trace [options]");
 	CommandLine::option_handle HELP =
 		cmd.addOption("h", "help", Arg::None, "-h/--help \tPrint usage and exit");
 	CommandLine::option_handle TRACE_FILE =
@@ -176,9 +177,15 @@ int main(int argc, char *argv[]) {
 	// reparse all arguments.
 	cmd.parse();
 
-	if (cmd[HELP]) {
+	if (cmd[HELP] || cmd[UNKNOWN] || cmd.parser()->nonOptionsCount() > 0) {
+		for (option::Option* opt = cmd[UNKNOWN]; opt; opt = opt->next()) {
+			std::cerr << "Unknown option: " << opt->name << "\n";
+		}
+		for (int i = 0; i < cmd.parser()->nonOptionsCount(); ++i) {
+			std::cerr << "Unknown non-option: " << cmd.parser()->nonOption(i) << "\n";
+		}
 		cmd.printUsage();
-		exit(0);
+		exit(!cmd[HELP]);
 	}
 
 	if (cmd[TRACE_FILE]) {
diff --git a/tools/prune-trace/main.cc b/tools/prune-trace/main.cc
index 1bcd96ec..5c9129e9 100644
--- a/tools/prune-trace/main.cc
+++ b/tools/prune-trace/main.cc
@@ -35,7 +35,8 @@ int main(int argc, char *argv[]) {
 		cmd.add_args(argv[i]);
 	}
 
-	cmd.addOption("", "", Arg::None, "USAGE: prune-trace [options]");
+	CommandLine::option_handle UNKNOWN =
+		cmd.addOption("", "", Arg::None, "USAGE: prune-trace [options]");
 	CommandLine::option_handle HELP = cmd.addOption("h", "help", Arg::None, "-h,--help \tPrint usage and exit");
 
 	Database::cmdline_setup();
@@ -112,9 +113,15 @@ int main(int argc, char *argv[]) {
 	// reparse all arguments.
 	cmd.parse();
 
-	if (cmd[HELP]) {
+	if (cmd[HELP] || cmd[UNKNOWN] || cmd.parser()->nonOptionsCount() > 0) {
+		for (option::Option* opt = cmd[UNKNOWN]; opt; opt = opt->next()) {
+			std::cerr << "Unknown option: " << opt->name << "\n";
+		}
+		for (int i = 0; i < cmd.parser()->nonOptionsCount(); ++i) {
+			std::cerr << "Unknown non-option: " << cmd.parser()->nonOption(i) << "\n";
+		}
 		cmd.printUsage();
-		exit(0);
+		exit(!cmd[HELP]);
 	}
 
 	Database *db = Database::cmdline_connect();