diff --git a/apps/apps.c b/apps/apps.c
index 367eb177e..498722a5a 100644
--- a/apps/apps.c
+++ b/apps/apps.c
@@ -2428,7 +2428,7 @@ static void readbn(BIGNUM **bn, BIO *bconn)
 	int l;
 
 	l = BIO_gets(bconn, buf, sizeof buf);
-	assert(l >= 0);
+	assert(l > 0);
 	assert(buf[l-1] == '\n');
 	buf[l-1] = '\0';
 	BN_hex2bn(bn, buf);