diff --git a/qemu/include/qapi/visitor-impl.h b/qemu/include/qapi/visitor-impl.h
index 60be6b73..be1d1ed6 100644
--- a/qemu/include/qapi/visitor-impl.h
+++ b/qemu/include/qapi/visitor-impl.h
@@ -15,6 +15,17 @@
 #include "qapi/error.h"
 #include "qapi/visitor.h"
 
+/*
+ * There are three classes of visitors; setting the class determines
+ * how QAPI enums are visited, as well as what additional restrictions
+ * can be asserted.
+ */
+typedef enum VisitorType {
+    VISITOR_INPUT,
+    VISITOR_OUTPUT,
+    VISITOR_DEALLOC,
+} VisitorType;
+
 struct Visitor
 {
     /* Must be set */
@@ -30,12 +41,9 @@ struct Visitor
     GenericList *(*next_list)(Visitor *v, GenericList **list);
     void (*end_list)(Visitor *v);
 
-    void (*type_enum)(Visitor *v, const char *name, int *obj,
-                      const char *const strings[], Error **errp);
     /* May be NULL; only needed for input visitors. */
     void (*get_next_type)(Visitor *v, const char *name, QType *type,
                           bool promote_int, Error **errp);
-    /* Must be set. */
     void (*type_int64)(Visitor *v, const char *name, int64_t *obj,
                        Error **errp);
     /* Must be set. */
@@ -54,11 +62,9 @@ struct Visitor
 
     /* May be NULL; most useful for input visitors. */
     void (*optional)(Visitor *v, const char *name, bool *present);
+
+    /* Must be set */
+    VisitorType type;
 };
 
-void input_type_enum(Visitor *v, const char *name, int *obj,
-                     const char *const strings[], Error **errp);
-void output_type_enum(Visitor *v, const char *name, int *obj,
-                     const char *const strings[], Error **errp);
-
 #endif
diff --git a/qemu/include/qapi/visitor.h b/qemu/include/qapi/visitor.h
index 621b8b08..1cf4634d 100644
--- a/qemu/include/qapi/visitor.h
+++ b/qemu/include/qapi/visitor.h
@@ -53,8 +53,19 @@ bool visit_optional(Visitor *v, const char *name, bool *present);
  */
 void visit_get_next_type(Visitor *v, const char *name, QType *type,
                          bool promote_int, Error **errp);
+/*
+ * Visit an enum value.
+ *
+ * @strings expresses the mapping between C enum values and QAPI enum
+ * names; it should be the ENUM_lookup array from visit-types.h.
+ *
+ * May call visit_type_str() under the hood, and the enum visit may
+ * fail even if the corresponding string visit succeeded; this implies
+ * that visit_type_str() must have no unwelcome side effects.
+ */
 void visit_type_enum(Visitor *v, const char *name, int *obj,
                      const char *const strings[], Error **errp);
+
 void visit_type_int(Visitor *v, const char *name, int64_t *obj, Error **errp);
 void visit_type_uint8(Visitor *v, const char *name, uint8_t *obj,
                       Error **errp);
diff --git a/qemu/qapi/qapi-dealloc-visitor.c b/qemu/qapi/qapi-dealloc-visitor.c
index 0152f0fa..e1bb5718 100644
--- a/qemu/qapi/qapi-dealloc-visitor.c
+++ b/qemu/qapi/qapi-dealloc-visitor.c
@@ -169,11 +169,6 @@ static void qapi_dealloc_type_size(Visitor *v, const char *name, uint64_t *obj,
 {
 }
 
-static void qapi_dealloc_type_enum(Visitor *v, const char *name, int *obj,
-                                   const char * const strings[], Error **errp)
-{
-}
-
 Visitor *qapi_dealloc_get_visitor(QapiDeallocVisitor *v)
 {
     return &v->visitor;
@@ -190,6 +185,7 @@ QapiDeallocVisitor *qapi_dealloc_visitor_new(void)
 
     v = g_malloc0(sizeof(*v));
 
+    v->visitor.type = VISITOR_DEALLOC;
     v->visitor.start_struct = qapi_dealloc_start_struct;
     v->visitor.end_struct = qapi_dealloc_end_struct;
     v->visitor.start_implicit_struct = qapi_dealloc_start_implicit_struct;
@@ -197,7 +193,6 @@ QapiDeallocVisitor *qapi_dealloc_visitor_new(void)
     v->visitor.start_list = qapi_dealloc_start_list;
     v->visitor.next_list = qapi_dealloc_next_list;
     v->visitor.end_list = qapi_dealloc_end_list;
-    v->visitor.type_enum = qapi_dealloc_type_enum;
     v->visitor.type_int64 = qapi_dealloc_type_int64;
     v->visitor.type_uint64 = qapi_dealloc_type_uint64;
     v->visitor.type_bool = qapi_dealloc_type_bool;
diff --git a/qemu/qapi/qapi-visit-core.c b/qemu/qapi/qapi-visit-core.c
index f8680b42..59b01bb1 100644
--- a/qemu/qapi/qapi-visit-core.c
+++ b/qemu/qapi/qapi-visit-core.c
@@ -78,12 +78,6 @@ void visit_get_next_type(Visitor *v, const char *name, QType *type,
     }
 }
 
-void visit_type_enum(Visitor *v, const char *name, int *obj,
-                     const char *const strings[], Error **errp)
-{
-    v->type_enum(v, name, obj, strings, errp);
-}
-
 void visit_type_int(Visitor *v, const char *name, int64_t *obj, Error **errp)
 {
     v->type_int64(v, name, obj, errp);
@@ -211,14 +205,13 @@ void visit_type_any(Visitor *v, const char *name, QObject **obj, Error **errp)
     v->type_any(v, name, obj, errp);
 }
 
-void output_type_enum(Visitor *v, const char *name, int *obj,
-                      const char *const strings[], Error **errp)
+static void output_type_enum(Visitor *v, const char *name, int *obj,
+                             const char *const strings[], Error **errp)
 {
     int i = 0;
     int value = *obj;
     char *enum_str;
 
-    assert(strings);
     while (strings[i++] != NULL);
     if (value < 0 || value >= i - 1) {
         error_setg(errp, QERR_INVALID_PARAMETER, name ? name : "null");
@@ -229,15 +222,13 @@ void output_type_enum(Visitor *v, const char *name, int *obj,
     visit_type_str(v, name, &enum_str, errp);
 }
 
-void input_type_enum(Visitor *v, const char *name, int *obj,
-                     const char *const strings[], Error **errp)
+static void input_type_enum(Visitor *v, const char *name, int *obj,
+                            const char *const strings[], Error **errp)
 {
     Error *local_err = NULL;
     int64_t value = 0;
     char *enum_str;
 
-    assert(strings);
-
     visit_type_str(v, name, &enum_str, &local_err);
     if (local_err) {
         error_propagate(errp, local_err);
@@ -260,3 +251,14 @@ void input_type_enum(Visitor *v, const char *name, int *obj,
     g_free(enum_str);
     *obj = (int)value;
 }
+
+void visit_type_enum(Visitor *v, const char *name, int *obj,
+                     const char *const strings[], Error **errp)
+{
+    assert(strings);
+    if (v->type == VISITOR_INPUT) {
+        input_type_enum(v, name, obj, strings, errp);
+    } else if (v->type == VISITOR_OUTPUT) {
+        output_type_enum(v, name, obj, strings, errp);
+    }
+}
diff --git a/qemu/qapi/qmp-input-visitor.c b/qemu/qapi/qmp-input-visitor.c
index 0c6fbbee..3fb9f0e9 100644
--- a/qemu/qapi/qmp-input-visitor.c
+++ b/qemu/qapi/qmp-input-visitor.c
@@ -350,6 +350,7 @@ QmpInputVisitor *qmp_input_visitor_new(QObject *obj)
 
     v = g_malloc0(sizeof(*v));
 
+    v->visitor.type = VISITOR_INPUT;
     v->visitor.start_struct = qmp_input_start_struct;
     v->visitor.end_struct = qmp_input_end_struct;
     v->visitor.start_implicit_struct = qmp_input_start_implicit_struct;
@@ -357,7 +358,6 @@ QmpInputVisitor *qmp_input_visitor_new(QObject *obj)
     v->visitor.start_list = qmp_input_start_list;
     v->visitor.next_list = qmp_input_next_list;
     v->visitor.end_list = qmp_input_end_list;
-    v->visitor.type_enum = input_type_enum;
     v->visitor.type_int64 = qmp_input_type_int64;
     v->visitor.type_uint64 = qmp_input_type_uint64;
     v->visitor.type_bool = qmp_input_type_bool;
diff --git a/qemu/qapi/qmp-output-visitor.c b/qemu/qapi/qmp-output-visitor.c
index c0c7c551..af8d1866 100644
--- a/qemu/qapi/qmp-output-visitor.c
+++ b/qemu/qapi/qmp-output-visitor.c
@@ -234,12 +234,12 @@ QmpOutputVisitor *qmp_output_visitor_new(void)
 
     v = g_malloc0(sizeof(*v));
 
+    v->visitor.type = VISITOR_OUTPUT;
     v->visitor.start_struct = qmp_output_start_struct;
     v->visitor.end_struct = qmp_output_end_struct;
     v->visitor.start_list = qmp_output_start_list;
     v->visitor.next_list = qmp_output_next_list;
     v->visitor.end_list = qmp_output_end_list;
-    v->visitor.type_enum = output_type_enum;
     v->visitor.type_int64 = qmp_output_type_int64;
     v->visitor.type_uint64 = qmp_output_type_uint64;
     v->visitor.type_bool = qmp_output_type_bool;
diff --git a/qemu/qapi/string-input-visitor.c b/qemu/qapi/string-input-visitor.c
index 7d5fe5c9..d695f072 100644
--- a/qemu/qapi/string-input-visitor.c
+++ b/qemu/qapi/string-input-visitor.c
@@ -328,7 +328,7 @@ StringInputVisitor *string_input_visitor_new(const char *str)
 
     v = g_malloc0(sizeof(*v));
 
-    v->visitor.type_enum = input_type_enum;
+    v->visitor.type = VISITOR_INPUT;
     v->visitor.type_int64 = parse_type_int64;
     v->visitor.type_uint64 = parse_type_uint64;
     v->visitor.type_size = NULL;