diff --git a/glib/gvariant.c b/glib/gvariant.c
index e48dec1ad..8ebbaa662 100644
--- a/glib/gvariant.c
+++ b/glib/gvariant.c
@@ -5944,7 +5944,7 @@ g_variant_byteswap (GVariant *value)
   if (alignment)
     /* (potentially) contains multi-byte numeric data */
     {
-      GVariantSerialised serialised;
+      GVariantSerialised serialised = { 0, };
       GVariant *trusted;
       GBytes *bytes;
 
diff --git a/glib/tests/gvariant.c b/glib/tests/gvariant.c
index 35434cae9..ebd617639 100644
--- a/glib/tests/gvariant.c
+++ b/glib/tests/gvariant.c
@@ -1438,7 +1438,7 @@ test_maybe (void)
 
     for (flavour = 0; flavour < 8; flavour += alignment)
       {
-        GVariantSerialised serialised;
+        GVariantSerialised serialised = { 0, };
         GVariantSerialised child;
 
         serialised.type_info = type_info;
@@ -1562,7 +1562,7 @@ test_array (void)
 
     for (flavour = 0; flavour < 8; flavour += alignment)
       {
-        GVariantSerialised serialised;
+        GVariantSerialised serialised = { 0, };
 
         serialised.type_info = array_info;
         serialised.data = flavoured_malloc (needed_size, flavour);
@@ -1726,7 +1726,7 @@ test_tuple (void)
 
     for (flavour = 0; flavour < 8; flavour += alignment)
       {
-        GVariantSerialised serialised;
+        GVariantSerialised serialised = { 0, };
 
         serialised.type_info = type_info;
         serialised.data = flavoured_malloc (needed_size, flavour);
@@ -1821,7 +1821,7 @@ test_variant (void)
 
     for (flavour = 0; flavour < 8; flavour += alignment)
       {
-        GVariantSerialised serialised;
+        GVariantSerialised serialised = { 0, };
         GVariantSerialised child;
 
         serialised.type_info = type_info;
@@ -2268,7 +2268,7 @@ serialise_tree (TreeInstance       *tree,
 static void
 test_byteswap (void)
 {
-  GVariantSerialised one, two;
+  GVariantSerialised one = { 0, }, two = { 0, };
   TreeInstance *tree;
 
   tree = tree_instance_new (NULL, 3);
@@ -2342,7 +2342,7 @@ test_serialiser_children (void)
 static void
 test_fuzz (gdouble *fuzziness)
 {
-  GVariantSerialised serialised;
+  GVariantSerialised serialised = { 0, };
   TreeInstance *tree;
 
   /* make an instance */