diff --git a/scripts/checkincludes.pl b/scripts/checkincludes.pl
index 32ebff6..4bff139 100755
--- a/scripts/checkincludes.pl
+++ b/scripts/checkincludes.pl
@@ -3,6 +3,15 @@
 # checkincludes: Find files included more than once in (other) files.
 # Copyright abandoned, 2000, Niels Kristian Bech Jensen <nkbj@image.dk>.
 
+sub usage {
+	print "Usage: checkincludes.pl <file list>\n";
+	exit 1;
+}
+
+if ($#ARGV < 0) {
+        usage();
+}
+
 foreach $file (@ARGV) {
 	open(FILE, $file) or die "Cannot open $file: $!.\n";