diff --git a/docs/storage.html.in b/docs/storage.html.in
index f920dae00f..b9b503de82 100644
--- a/docs/storage.html.in
+++ b/docs/storage.html.in
@@ -346,6 +346,7 @@
       on the size and placement of volumes. The 'free extents'
       information will detail the regions which are available for creating
       new volumes. A volume cannot span across 2 different free extents.
+      It will default to using <code>msdos</code> as the pool source format.
     </p>
 
     <h3>Example pool input</h3>
diff --git a/src/storage/storage_backend_disk.c b/src/storage/storage_backend_disk.c
index 3309a936c4..ba928d84e7 100644
--- a/src/storage/storage_backend_disk.c
+++ b/src/storage/storage_backend_disk.c
@@ -468,13 +468,20 @@ virStorageBackendDiskBuildPool(virConnectPtr conn ATTRIBUTE_UNUSED,
     }
 
     if (ok_to_mklabel) {
-        /* eg parted /dev/sda mklabel msdos */
+        /* eg parted /dev/sda mklabel --script msdos */
+        int format = pool->def->source.format;
+        const char *fmt;
+        if (format == VIR_STORAGE_POOL_DISK_UNKNOWN ||
+            format == VIR_STORAGE_POOL_DISK_DOS)
+            fmt = "msdos";
+        else
+            fmt = virStoragePoolFormatDiskTypeToString(format);
+
         cmd = virCommandNewArgList(PARTED,
                                    pool->def->source.devices[0].path,
                                    "mklabel",
                                    "--script",
-                                   ((pool->def->source.format == VIR_STORAGE_POOL_DISK_DOS) ? "msdos" :
-                                   virStoragePoolFormatDiskTypeToString(pool->def->source.format)),
+                                   fmt,
                                    NULL);
         ret = virCommandRun(cmd, NULL);
     }