diff --git a/bin/qemu b/bin/qemu
index 5e3f00d..3fefbd1 100755
--- a/bin/qemu
+++ b/bin/qemu
@@ -87,6 +87,10 @@ dtb_args()
 
 mnt_args()
 {
+    if [ -z "${QEMU_MNT}" ]; then
+	return
+    fi
+
     echo -n "-device ${QEMU_SCSI},id=scsi0 "
     echo -n "-device scsi-hd,bus=scsi0.0,drive=drive0 "
     echo -n "-drive file=${QEMU_MNT},if=none,format=raw,discard=unmap,id=drive0 "
@@ -94,6 +98,10 @@ mnt_args()
 
 host_args()
 {
+    if [ -z "${QEMU_HOST}" ]; then
+	return
+    fi
+
     echo -n "-virtfs local,id=hosfts,path=${QEMU_HOST},security_model=none,mount_tag=hostfs "
 }