diff --git a/block/gluster.c b/block/gluster.c
index dc16f0c329..62f8ff2147 100644
--- a/block/gluster.c
+++ b/block/gluster.c
@@ -98,7 +98,14 @@ static QemuOptsList qemu_gluster_create_opts = {
         {
             .name = BLOCK_OPT_PREALLOC,
             .type = QEMU_OPT_STRING,
-            .help = "Preallocation mode (allowed values: off, full)"
+            .help = "Preallocation mode (allowed values: off"
+#ifdef CONFIG_GLUSTERFS_FALLOCATE
+                    ", falloc"
+#endif
+#ifdef CONFIG_GLUSTERFS_ZEROFILL
+                    ", full"
+#endif
+                    ")"
         },
         {
             .name = GLUSTER_OPT_DEBUG,