diff --git a/include/qapi/visitor-impl.h b/include/qapi/visitor-impl.h
index ea252f8e3a525bca3650ea11086e45738ef9de81..7905a2845e2d2ec1c5d8b9cb143e849c14ef363a 100644
--- a/include/qapi/visitor-impl.h
+++ b/include/qapi/visitor-impl.h
@@ -29,7 +29,7 @@ struct Visitor
 
     void (*start_list)(Visitor *v, const char *name, Error **errp);
     /* Must be set */
-    GenericList *(*next_list)(Visitor *v, GenericList **list);
+    GenericList *(*next_list)(Visitor *v, GenericList **list, size_t size);
     /* Must be set */
     void (*end_list)(Visitor *v);
 
diff --git a/include/qapi/visitor.h b/include/qapi/visitor.h
index 5e581dcf7e1d073464ab56ec662f9420c5ed6c2b..8a2d5ccaccc7d6c3b41ec66b8985a8e37d11d78b 100644
--- a/include/qapi/visitor.h
+++ b/include/qapi/visitor.h
@@ -19,13 +19,12 @@
 #include "qapi/error.h"
 #include <stdlib.h>
 
-typedef struct GenericList
-{
-    union {
-        void *value;
-        uint64_t padding;
-    };
+/* This struct is layout-compatible with all other *List structs
+ * created by the qapi generator.  It is used as a typical
+ * singly-linked list. */
+typedef struct GenericList {
     struct GenericList *next;
+    char padding[];
 } GenericList;
 
 void visit_start_struct(Visitor *v, const char *name, void **obj,
@@ -36,7 +35,7 @@ void visit_start_implicit_struct(Visitor *v, void **obj, size_t size,
 void visit_end_implicit_struct(Visitor *v);
 
 void visit_start_list(Visitor *v, const char *name, Error **errp);
-GenericList *visit_next_list(Visitor *v, GenericList **list);
+GenericList *visit_next_list(Visitor *v, GenericList **list, size_t size);
 void visit_end_list(Visitor *v);
 
 /**
diff --git a/qapi/opts-visitor.c b/qapi/opts-visitor.c
index ae5b9553fa133befae12f9e5c4411248de8bece5..73e4acea7b4bfa724b69c6a818572f83e1d51574 100644
--- a/qapi/opts-visitor.c
+++ b/qapi/opts-visitor.c
@@ -215,7 +215,7 @@ opts_start_list(Visitor *v, const char *name, Error **errp)
 
 
 static GenericList *
-opts_next_list(Visitor *v, GenericList **list)
+opts_next_list(Visitor *v, GenericList **list, size_t size)
 {
     OptsVisitor *ov = to_ov(v);
     GenericList **link;
@@ -258,7 +258,7 @@ opts_next_list(Visitor *v, GenericList **list)
         abort();
     }
 
-    *link = g_malloc0(sizeof **link);
+    *link = g_malloc0(size);
     return *link;
 }
 
diff --git a/qapi/qapi-dealloc-visitor.c b/qapi/qapi-dealloc-visitor.c
index 2659d3fcca6c13e79c00a152f8e5239fa598bc16..6667e8ca437fe6daf81bb17e92bf7be9063d9cbe 100644
--- a/qapi/qapi-dealloc-visitor.c
+++ b/qapi/qapi-dealloc-visitor.c
@@ -100,7 +100,8 @@ static void qapi_dealloc_start_list(Visitor *v, const char *name, Error **errp)
     qapi_dealloc_push(qov, NULL);
 }
 
-static GenericList *qapi_dealloc_next_list(Visitor *v, GenericList **listp)
+static GenericList *qapi_dealloc_next_list(Visitor *v, GenericList **listp,
+                                           size_t size)
 {
     GenericList *list = *listp;
     QapiDeallocVisitor *qov = to_qov(v);
diff --git a/qapi/qapi-visit-core.c b/qapi/qapi-visit-core.c
index f8562864613c9fc8a9b1e74229021deaca63c14e..b4a0f21b36ade10de21cdc717d888200e4800d99 100644
--- a/qapi/qapi-visit-core.c
+++ b/qapi/qapi-visit-core.c
@@ -50,9 +50,10 @@ void visit_start_list(Visitor *v, const char *name, Error **errp)
     v->start_list(v, name, errp);
 }
 
-GenericList *visit_next_list(Visitor *v, GenericList **list)
+GenericList *visit_next_list(Visitor *v, GenericList **list, size_t size)
 {
-    return v->next_list(v, list);
+    assert(list && size >= sizeof(GenericList));
+    return v->next_list(v, list, size);
 }
 
 void visit_end_list(Visitor *v)
diff --git a/qapi/qmp-input-visitor.c b/qapi/qmp-input-visitor.c
index 2f48b95515b736f27e8da7130941a2615a111369..26216604ccb4429cd327932b5fb6304a124bbf2f 100644
--- a/qapi/qmp-input-visitor.c
+++ b/qapi/qmp-input-visitor.c
@@ -165,7 +165,8 @@ static void qmp_input_start_list(Visitor *v, const char *name, Error **errp)
     qmp_input_push(qiv, qobj, errp);
 }
 
-static GenericList *qmp_input_next_list(Visitor *v, GenericList **list)
+static GenericList *qmp_input_next_list(Visitor *v, GenericList **list,
+                                        size_t size)
 {
     QmpInputVisitor *qiv = to_qiv(v);
     GenericList *entry;
@@ -184,7 +185,7 @@ static GenericList *qmp_input_next_list(Visitor *v, GenericList **list)
         return NULL;
     }
 
-    entry = g_malloc0(sizeof(*entry));
+    entry = g_malloc0(size);
     if (first) {
         *list = entry;
     } else {
diff --git a/qapi/qmp-output-visitor.c b/qapi/qmp-output-visitor.c
index f47eefa626183cf016600d23a793f11ec63db5ed..d44c676317d033cc5b264a36921c1a75ceaa61f8 100644
--- a/qapi/qmp-output-visitor.c
+++ b/qapi/qmp-output-visitor.c
@@ -126,7 +126,8 @@ static void qmp_output_start_list(Visitor *v, const char *name, Error **errp)
     qmp_output_push(qov, list);
 }
 
-static GenericList *qmp_output_next_list(Visitor *v, GenericList **listp)
+static GenericList *qmp_output_next_list(Visitor *v, GenericList **listp,
+                                         size_t size)
 {
     GenericList *list = *listp;
     QmpOutputVisitor *qov = to_qov(v);
diff --git a/qapi/string-input-visitor.c b/qapi/string-input-visitor.c
index 18b9339768de3986e07d4325f6b97146abf5488e..59eb5dc4e3b5b25075fcbdac9900c58c9fae2f8c 100644
--- a/qapi/string-input-visitor.c
+++ b/qapi/string-input-visitor.c
@@ -139,7 +139,7 @@ start_list(Visitor *v, const char *name, Error **errp)
     }
 }
 
-static GenericList *next_list(Visitor *v, GenericList **list)
+static GenericList *next_list(Visitor *v, GenericList **list, size_t size)
 {
     StringInputVisitor *siv = to_siv(v);
     GenericList **link;
@@ -173,7 +173,7 @@ static GenericList *next_list(Visitor *v, GenericList **list)
         link = &(*list)->next;
     }
 
-    *link = g_malloc0(sizeof **link);
+    *link = g_malloc0(size);
     return *link;
 }
 
diff --git a/qapi/string-output-visitor.c b/qapi/string-output-visitor.c
index b980bd3265f24c56016277541eeb300c6ad4b127..c2e5c5b92b2c890f9f9c110ec0f77d57d2939725 100644
--- a/qapi/string-output-visitor.c
+++ b/qapi/string-output-visitor.c
@@ -276,7 +276,7 @@ start_list(Visitor *v, const char *name, Error **errp)
     sov->head = true;
 }
 
-static GenericList *next_list(Visitor *v, GenericList **list)
+static GenericList *next_list(Visitor *v, GenericList **list, size_t size)
 {
     StringOutputVisitor *sov = to_sov(v);
     GenericList *ret = NULL;
diff --git a/scripts/qapi-types.py b/scripts/qapi-types.py
index 7b0dca8c72dd6d464b9101958273b982473f40b1..83f230a662f7dd3657105ce9342d063f748ff4ce 100644
--- a/scripts/qapi-types.py
+++ b/scripts/qapi-types.py
@@ -26,11 +26,8 @@ def gen_array(name, element_type):
     return mcgen('''
 
 struct %(c_name)s {
-    union {
-        %(c_type)s value;
-        uint64_t padding;
-    };
     %(c_name)s *next;
+    %(c_type)s value;
 };
 ''',
                  c_name=c_name(name), c_type=element_type.c_type())
diff --git a/scripts/qapi-visit.py b/scripts/qapi-visit.py
index a8b1057f842f74b0daf8eac5fe289224bfa37d8e..dfeef7196bfb239cc83412c8b6fbbb8bd01288e2 100644
--- a/scripts/qapi-visit.py
+++ b/scripts/qapi-visit.py
@@ -173,7 +173,7 @@ void visit_type_%(c_name)s(Visitor *v, const char *name, %(c_name)s **obj, Error
     }
 
     for (prev = (GenericList **)obj;
-         !err && (i = visit_next_list(v, prev)) != NULL;
+         !err && (i = visit_next_list(v, prev, sizeof(**obj))) != NULL;
          prev = &i) {
         %(c_name)s *native_i = (%(c_name)s *)i;
         visit_type_%(c_elt_type)s(v, NULL, &native_i->value, &err);