diff --git a/gio/gvdb/gvdb-builder.c b/gio/gvdb/gvdb-builder.c
index 45c5f4b38..e13924349 100644
--- a/gio/gvdb/gvdb-builder.c
+++ b/gio/gvdb/gvdb-builder.c
@@ -474,7 +474,7 @@ static GString *
 file_builder_serialise (FileBuilder          *fb,
                         struct gvdb_pointer   root)
 {
-  struct gvdb_header header;
+  struct gvdb_header header = { { 0, }, };
   GString *result;
 
   if (fb->byteswap)