diff --git a/src/launch-libvirt.c b/src/launch-libvirt.c
index f6fa36f04..c055504a1 100644
--- a/src/launch-libvirt.c
+++ b/src/launch-libvirt.c
@@ -1103,11 +1103,13 @@ construct_libvirt_xml_qemu_cmdline (guestfs_h *g, xmlTextWriterPtr xo)
                                            BAD_CAST qp->qemu_param));
     XMLERROR (-1, xmlTextWriterEndElement (xo));
 
-    XMLERROR (-1, xmlTextWriterStartElement (xo, BAD_CAST "qemu:arg"));
-    XMLERROR (-1,
-              xmlTextWriterWriteAttribute (xo, BAD_CAST "value",
-                                           BAD_CAST qp->qemu_value));
-    XMLERROR (-1, xmlTextWriterEndElement (xo));
+    if (qp->qemu_value) {
+      XMLERROR (-1, xmlTextWriterStartElement (xo, BAD_CAST "qemu:arg"));
+      XMLERROR (-1,
+                xmlTextWriterWriteAttribute (xo, BAD_CAST "value",
+                                             BAD_CAST qp->qemu_value));
+      XMLERROR (-1, xmlTextWriterEndElement (xo));
+    }
   }
 
   XMLERROR (-1, xmlTextWriterEndElement (xo));
diff --git a/src/launch.c b/src/launch.c
index 7ca6fe11b..a0d6c121f 100644
--- a/src/launch.c
+++ b/src/launch.c
@@ -320,7 +320,7 @@ guestfs__config (guestfs_h *g,
 
   qp = safe_malloc (g, sizeof *qp);
   qp->qemu_param = safe_strdup (g, qemu_param);
-  qp->qemu_value = safe_strdup (g, qemu_value);
+  qp->qemu_value = qemu_value ? safe_strdup (g, qemu_value) : NULL;
 
   qp->next = g->qemu_params;
   g->qemu_params = qp;