diff --git a/include/qapi/visitor.h b/include/qapi/visitor.h
index 1fef18c08f..28c21d8338 100644
--- a/include/qapi/visitor.h
+++ b/include/qapi/visitor.h
@@ -18,7 +18,10 @@
 
 typedef struct GenericList
 {
-    void *value;
+    union {
+        void *value;
+        uint64_t padding;
+    };
     struct GenericList *next;
 } GenericList;
 
diff --git a/scripts/qapi-types.py b/scripts/qapi-types.py
index fd42d71da1..ddcfed9f4b 100644
--- a/scripts/qapi-types.py
+++ b/scripts/qapi-types.py
@@ -22,7 +22,10 @@ def generate_fwd_struct(name, members, builtin_type=False):
 
 typedef struct %(name)sList
 {
-    %(type)s value;
+    union {
+        %(type)s value;
+        uint64_t padding;
+    };
     struct %(name)sList *next;
 } %(name)sList;
 ''',
@@ -35,7 +38,10 @@ typedef struct %(name)s %(name)s;
 
 typedef struct %(name)sList
 {
-    %(name)s *value;
+    union {
+        %(name)s *value;
+        uint64_t padding;
+    };
     struct %(name)sList *next;
 } %(name)sList;
 ''',
diff --git a/target-i386/arch_memory_mapping.c b/target-i386/arch_memory_mapping.c
index 844893f44d..5096fbdf44 100644
--- a/target-i386/arch_memory_mapping.c
+++ b/target-i386/arch_memory_mapping.c
@@ -38,7 +38,7 @@ static void walk_pte(MemoryMappingList *list, hwaddr pte_start_addr,
             continue;
         }
 
-        start_vaddr = start_line_addr | ((i & 0x1fff) << 12);
+        start_vaddr = start_line_addr | ((i & 0x1ff) << 12);
         memory_mapping_list_add_merge_sorted(list, start_paddr,
                                              start_vaddr, 1 << 12);
     }
@@ -75,6 +75,8 @@ static void walk_pte2(MemoryMappingList *list,
 }
 
 /* PAE Paging or IA-32e Paging */
+#define PLM4_ADDR_MASK 0xffffffffff000 /* selects bits 51:12 */
+
 static void walk_pde(MemoryMappingList *list, hwaddr pde_start_addr,
                      int32_t a20_mask, target_ulong start_line_addr)
 {
@@ -105,7 +107,7 @@ static void walk_pde(MemoryMappingList *list, hwaddr pde_start_addr,
             continue;
         }
 
-        pte_start_addr = (pde & ~0xfff) & a20_mask;
+        pte_start_addr = (pde & PLM4_ADDR_MASK) & a20_mask;
         walk_pte(list, pte_start_addr, a20_mask, line_addr);
     }
 }
@@ -208,7 +210,7 @@ static void walk_pdpe(MemoryMappingList *list,
             continue;
         }
 
-        pde_start_addr = (pdpe & ~0xfff) & a20_mask;
+        pde_start_addr = (pdpe & PLM4_ADDR_MASK) & a20_mask;
         walk_pde(list, pde_start_addr, a20_mask, line_addr);
     }
 }
@@ -231,7 +233,7 @@ static void walk_pml4e(MemoryMappingList *list,
         }
 
         line_addr = ((i & 0x1ffULL) << 39) | (0xffffULL << 48);
-        pdpe_start_addr = (pml4e & ~0xfff) & a20_mask;
+        pdpe_start_addr = (pml4e & PLM4_ADDR_MASK) & a20_mask;
         walk_pdpe(list, pdpe_start_addr, a20_mask, line_addr);
     }
 }
@@ -249,7 +251,7 @@ int cpu_get_memory_mapping(MemoryMappingList *list, CPUArchState *env)
         if (env->hflags & HF_LMA_MASK) {
             hwaddr pml4e_addr;
 
-            pml4e_addr = (env->cr[3] & ~0xfff) & env->a20_mask;
+            pml4e_addr = (env->cr[3] & PLM4_ADDR_MASK) & env->a20_mask;
             walk_pml4e(list, pml4e_addr, env->a20_mask);
         } else
 #endif
diff --git a/tests/test-qmp-output-visitor.c b/tests/test-qmp-output-visitor.c
index 0942a41875..b2fa9a74f6 100644
--- a/tests/test-qmp-output-visitor.c
+++ b/tests/test-qmp-output-visitor.c
@@ -295,7 +295,10 @@ static void test_visitor_out_struct_errors(TestOutputVisitorData *data,
 
 typedef struct TestStructList
 {
-    TestStruct *value;
+    union {
+        TestStruct *value;
+        uint64_t padding;
+    };
     struct TestStructList *next;
 } TestStructList;