diff --git a/scripts/qapi-commands.py b/scripts/qapi-commands.py
index 4e99c1de8b..9d214a6609 100644
--- a/scripts/qapi-commands.py
+++ b/scripts/qapi-commands.py
@@ -101,7 +101,6 @@ def gen_marshal_input_visit(arg_type, dealloc=False):
         return ret
 
     if dealloc:
-        errparg = 'NULL'
         errarg = None
         ret += mcgen('''
     qmp_input_visitor_cleanup(qiv);
@@ -109,36 +108,12 @@ def gen_marshal_input_visit(arg_type, dealloc=False):
     v = qapi_dealloc_get_visitor(qdv);
 ''')
     else:
-        errparg = '&err'
         errarg = 'err'
         ret += mcgen('''
     v = qmp_input_get_visitor(qiv);
 ''')
 
-    for memb in arg_type.members:
-        if memb.optional:
-            ret += mcgen('''
-    visit_optional(v, &has_%(c_name)s, "%(name)s", %(errp)s);
-''',
-                         c_name=c_name(memb.name), name=memb.name,
-                         errp=errparg)
-            ret += gen_err_check(err=errarg)
-            ret += mcgen('''
-    if (has_%(c_name)s) {
-''',
-                         c_name=c_name(memb.name))
-            push_indent()
-        ret += mcgen('''
-    visit_type_%(c_type)s(v, &%(c_name)s, "%(name)s", %(errp)s);
-''',
-                     c_name=c_name(memb.name), name=memb.name,
-                     c_type=memb.type.c_name(), errp=errparg)
-        ret += gen_err_check(err=errarg)
-        if memb.optional:
-            pop_indent()
-            ret += mcgen('''
-    }
-''')
+    ret += gen_visit_fields(arg_type.members, errarg=errarg)
 
     if dealloc:
         ret += mcgen('''
diff --git a/scripts/qapi-event.py b/scripts/qapi-event.py
index eaaac05154..720486f06c 100644
--- a/scripts/qapi-event.py
+++ b/scripts/qapi-event.py
@@ -71,36 +71,7 @@ def gen_event_send(name, arg_type):
 ''',
                      name=name)
         ret += gen_err_check()
-
-        for memb in arg_type.members:
-            if memb.optional:
-                ret += mcgen('''
-    if (has_%(c_name)s) {
-''',
-                             c_name=c_name(memb.name))
-                push_indent()
-
-            # Ugly: need to cast away the const
-            if memb.type.name == "str":
-                cast = '(char **)'
-            else:
-                cast = ''
-
-            ret += mcgen('''
-    visit_type_%(c_type)s(v, %(cast)s&%(c_name)s, "%(name)s", &err);
-''',
-                         cast=cast,
-                         c_name=c_name(memb.name),
-                         c_type=memb.type.c_name(),
-                         name=memb.name)
-            ret += gen_err_check()
-
-            if memb.optional:
-                pop_indent()
-                ret += mcgen('''
-    }
-''')
-
+        ret += gen_visit_fields(arg_type.members, need_cast=True)
         ret += mcgen('''
     visit_end_struct(v, &err);
     if (err) {
diff --git a/scripts/qapi-visit.py b/scripts/qapi-visit.py
index bc6911f8fe..4f97781348 100644
--- a/scripts/qapi-visit.py
+++ b/scripts/qapi-visit.py
@@ -85,27 +85,7 @@ static void visit_type_%(c_name)s_fields(Visitor *v, %(c_name)s **obj, Error **e
                      c_type=base.c_name(), c_name=c_name('base'))
         ret += gen_err_check()
 
-    for memb in members:
-        if memb.optional:
-            ret += mcgen('''
-    visit_optional(v, &(*obj)->has_%(c_name)s, "%(name)s", &err);
-    if (!err && (*obj)->has_%(c_name)s) {
-''',
-                         c_name=c_name(memb.name), name=memb.name)
-            push_indent()
-
-        ret += mcgen('''
-    visit_type_%(c_type)s(v, &(*obj)->%(c_name)s, "%(name)s", &err);
-''',
-                     c_type=memb.type.c_name(), c_name=c_name(memb.name),
-                     name=memb.name)
-
-        if memb.optional:
-            pop_indent()
-            ret += mcgen('''
-    }
-''')
-        ret += gen_err_check()
+    ret += gen_visit_fields(members, prefix='(*obj)->')
 
     if re.search('^ *goto out;', ret, re.MULTILINE):
         ret += mcgen('''
diff --git a/scripts/qapi.py b/scripts/qapi.py
index 62a415ccd9..ada6380db2 100644
--- a/scripts/qapi.py
+++ b/scripts/qapi.py
@@ -1548,6 +1548,49 @@ def gen_err_check(err='err', label='out'):
                  err=err, label=label)
 
 
+def gen_visit_fields(members, prefix='', need_cast=False, errarg='err'):
+    ret = ''
+    if errarg:
+        errparg = '&' + errarg
+    else:
+        errparg = 'NULL'
+
+    for memb in members:
+        if memb.optional:
+            ret += mcgen('''
+    visit_optional(v, &%(prefix)shas_%(c_name)s, "%(name)s", %(errp)s);
+''',
+                         prefix=prefix, c_name=c_name(memb.name),
+                         name=memb.name, errp=errparg)
+            ret += gen_err_check(err=errarg)
+            ret += mcgen('''
+    if (%(prefix)shas_%(c_name)s) {
+''',
+                         prefix=prefix, c_name=c_name(memb.name))
+            push_indent()
+
+        # Ugly: sometimes we need to cast away const
+        if need_cast and memb.type.name == 'str':
+            cast = '(char **)'
+        else:
+            cast = ''
+
+        ret += mcgen('''
+    visit_type_%(c_type)s(v, %(cast)s&%(prefix)s%(c_name)s, "%(name)s", %(errp)s);
+''',
+                     c_type=memb.type.c_name(), prefix=prefix, cast=cast,
+                     c_name=c_name(memb.name), name=memb.name,
+                     errp=errparg)
+        ret += gen_err_check(err=errarg)
+
+        if memb.optional:
+            pop_indent()
+            ret += mcgen('''
+    }
+''')
+    return ret
+
+
 #
 # Common command line parsing
 #