diff --git a/tar.c b/tar.c
index 9606515..31cc399 100644
--- a/tar.c
+++ b/tar.c
@@ -52,7 +52,7 @@ static ino_t tarinode;
 static dev_t tardev;
 
 static int  mflag;
-static char filtermode;
+static char filtermode = '\0';
 
 static FILE *
 decomp(FILE *fp)
@@ -348,6 +348,8 @@ main(int argc, char *argv[])
 
 	if (!mode || argc != (mode == 'c'))
 		usage();
+	if (mode == 'c' && filtermode)
+		usage();
 
 	switch (mode) {
 	case 'c':