diff --git a/cmp.c b/cmp.c
index c9d38f3..976bc00 100644
--- a/cmp.c
+++ b/cmp.c
@@ -37,7 +37,7 @@ main(int argc, char *argv[])
 	if (argc != 2)
 		usage();
 
-	if (argv[0][0] == '-')
+	if (argv[0][0] == '-' && !argv[0][1])
 		argv[0] = "/dev/fd/0";
 	fp[0] = fopen(argv[0], "r");
 	if (!fp[0]) {
@@ -46,7 +46,7 @@ main(int argc, char *argv[])
 		exit(Error);
 	}
 
-	if (argv[1][0] == '-')
+	if (argv[1][0] == '-' && !argv[1][1])
 		argv[1] = "/dev/fd/0";
 	fp[1] = fopen(argv[1], "r");
 	if (!fp[1]) {
diff --git a/comm.c b/comm.c
index 59cfc3d..a946cba 100644
--- a/comm.c
+++ b/comm.c
@@ -41,7 +41,7 @@ main(int argc, char *argv[])
 		usage();
 
 	for (i = 0; i < LEN(fp); i++) {
-		if (argv[i][0] == '-')
+		if (argv[i][0] == '-' && !argv[i][1])
 			argv[i] = "/dev/fd/0";
 		if (!(fp[i] = fopen(argv[i], "r")))
 			eprintf("fopen %s:", argv[i]);