diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index 9836972234d929a7b98b731073b22278e19f86d0..77f0d83054b33ab18f615347fed189e190874d23 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -1581,7 +1581,6 @@ qemuBuildDiskDeviceStr(const virDomainDef *def,
                        virQEMUCapsPtr qemuCaps)
 {
     g_auto(virBuffer) opt = VIR_BUFFER_INITIALIZER;
-    const char *bus = virDomainDiskQEMUBusTypeToString(disk->bus);
     const char *contAlias;
     g_autofree char *backendAlias = NULL;
     g_autofree char *scsiVPDDeviceId = NULL;
@@ -1838,7 +1837,8 @@ qemuBuildDiskDeviceStr(const virDomainDef *def,
     case VIR_DOMAIN_DISK_BUS_LAST:
     default:
         virReportError(VIR_ERR_INTERNAL_ERROR,
-                       _("unsupported disk bus '%s' with device setup"), bus);
+                       _("unsupported disk bus '%s' with device setup"),
+                       NULLSTR(virDomainDiskBusTypeToString(disk->bus)));
         return NULL;
     }