diff --git a/include/qapi/visitor-impl.h b/include/qapi/visitor-impl.h
index 319efe8..92c4bcb 100644
--- a/include/qapi/visitor-impl.h
+++ b/include/qapi/visitor-impl.h
@@ -40,6 +40,12 @@ struct Visitor
     void (*type_int64)(Visitor *v, int64_t *obj, const char *name,
                        Error **errp);
     /* Must be set. */
+    void (*type_uint64)(Visitor *v, uint64_t *obj, const char *name,
+                        Error **errp);
+    /* Optional; fallback is type_uint64().  */
+    void (*type_size)(Visitor *v, uint64_t *obj, const char *name,
+                      Error **errp);
+    /* Must be set. */
     void (*type_bool)(Visitor *v, bool *obj, const char *name, Error **errp);
     void (*type_str)(Visitor *v, char **obj, const char *name, Error **errp);
     void (*type_number)(Visitor *v, double *obj, const char *name,
@@ -53,12 +59,9 @@ struct Visitor
     void (*type_uint8)(Visitor *v, uint8_t *obj, const char *name, Error **errp);
     void (*type_uint16)(Visitor *v, uint16_t *obj, const char *name, Error **errp);
     void (*type_uint32)(Visitor *v, uint32_t *obj, const char *name, Error **errp);
-    void (*type_uint64)(Visitor *v, uint64_t *obj, const char *name, Error **errp);
     void (*type_int8)(Visitor *v, int8_t *obj, const char *name, Error **errp);
     void (*type_int16)(Visitor *v, int16_t *obj, const char *name, Error **errp);
     void (*type_int32)(Visitor *v, int32_t *obj, const char *name, Error **errp);
-    /* visit_type_size() falls back to (*type_uint64)() if type_size is unset */
-    void (*type_size)(Visitor *v, uint64_t *obj, const char *name, Error **errp);
     bool (*start_union)(Visitor *v, bool data_present, Error **errp);
 };
 
diff --git a/qapi/qapi-dealloc-visitor.c b/qapi/qapi-dealloc-visitor.c
index 07d7337..2c257d8 100644
--- a/qapi/qapi-dealloc-visitor.c
+++ b/qapi/qapi-dealloc-visitor.c
@@ -141,6 +141,11 @@ static void qapi_dealloc_type_int64(Visitor *v, int64_t *obj, const char *name,
 {
 }
 
+static void qapi_dealloc_type_uint64(Visitor *v, uint64_t *obj,
+                                     const char *name, Error **errp)
+{
+}
+
 static void qapi_dealloc_type_bool(Visitor *v, bool *obj, const char *name,
                                    Error **errp)
 {
@@ -216,6 +221,7 @@ QapiDeallocVisitor *qapi_dealloc_visitor_new(void)
     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;
     v->visitor.type_str = qapi_dealloc_type_str;
     v->visitor.type_number = qapi_dealloc_type_number;
diff --git a/qapi/qapi-visit-core.c b/qapi/qapi-visit-core.c
index 2446a12..afcd59b 100644
--- a/qapi/qapi-visit-core.c
+++ b/qapi/qapi-visit-core.c
@@ -97,14 +97,14 @@ void visit_type_int(Visitor *v, int64_t *obj, const char *name, Error **errp)
 
 void visit_type_uint8(Visitor *v, uint8_t *obj, const char *name, Error **errp)
 {
-    int64_t value;
+    uint64_t value;
 
     if (v->type_uint8) {
         v->type_uint8(v, obj, name, errp);
     } else {
         value = *obj;
-        v->type_int64(v, &value, name, errp);
-        if (value < 0 || value > UINT8_MAX) {
+        v->type_uint64(v, &value, name, errp);
+        if (value > UINT8_MAX) {
             /* FIXME questionable reuse of errp if callback changed
                value on error */
             error_setg(errp, QERR_INVALID_PARAMETER_VALUE,
@@ -117,14 +117,14 @@ void visit_type_uint8(Visitor *v, uint8_t *obj, const char *name, Error **errp)
 
 void visit_type_uint16(Visitor *v, uint16_t *obj, const char *name, Error **errp)
 {
-    int64_t value;
+    uint64_t value;
 
     if (v->type_uint16) {
         v->type_uint16(v, obj, name, errp);
     } else {
         value = *obj;
-        v->type_int64(v, &value, name, errp);
-        if (value < 0 || value > UINT16_MAX) {
+        v->type_uint64(v, &value, name, errp);
+        if (value > UINT16_MAX) {
             /* FIXME questionable reuse of errp if callback changed
                value on error */
             error_setg(errp, QERR_INVALID_PARAMETER_VALUE,
@@ -137,14 +137,14 @@ void visit_type_uint16(Visitor *v, uint16_t *obj, const char *name, Error **errp
 
 void visit_type_uint32(Visitor *v, uint32_t *obj, const char *name, Error **errp)
 {
-    int64_t value;
+    uint64_t value;
 
     if (v->type_uint32) {
         v->type_uint32(v, obj, name, errp);
     } else {
         value = *obj;
-        v->type_int64(v, &value, name, errp);
-        if (value < 0 || value > UINT32_MAX) {
+        v->type_uint64(v, &value, name, errp);
+        if (value > UINT32_MAX) {
             /* FIXME questionable reuse of errp if callback changed
                value on error */
             error_setg(errp, QERR_INVALID_PARAMETER_VALUE,
@@ -157,15 +157,7 @@ void visit_type_uint32(Visitor *v, uint32_t *obj, const char *name, Error **errp
 
 void visit_type_uint64(Visitor *v, uint64_t *obj, const char *name, Error **errp)
 {
-    int64_t value;
-
-    if (v->type_uint64) {
-        v->type_uint64(v, obj, name, errp);
-    } else {
-        value = *obj;
-        v->type_int64(v, &value, name, errp);
-        *obj = value;
-    }
+    v->type_uint64(v, obj, name, errp);
 }
 
 void visit_type_int8(Visitor *v, int8_t *obj, const char *name, Error **errp)
@@ -235,16 +227,10 @@ void visit_type_int64(Visitor *v, int64_t *obj, const char *name, Error **errp)
 
 void visit_type_size(Visitor *v, uint64_t *obj, const char *name, Error **errp)
 {
-    int64_t value;
-
     if (v->type_size) {
         v->type_size(v, obj, name, errp);
-    } else if (v->type_uint64) {
-        v->type_uint64(v, obj, name, errp);
     } else {
-        value = *obj;
-        v->type_int64(v, &value, name, errp);
-        *obj = value;
+        v->type_uint64(v, obj, name, errp);
     }
 }
 
diff --git a/qapi/qmp-input-visitor.c b/qapi/qmp-input-visitor.c
index d1668e3..5eb67df 100644
--- a/qapi/qmp-input-visitor.c
+++ b/qapi/qmp-input-visitor.c
@@ -240,6 +240,22 @@ static void qmp_input_type_int64(Visitor *v, int64_t *obj, const char *name,
     *obj = qint_get_int(qint);
 }
 
+static void qmp_input_type_uint64(Visitor *v, uint64_t *obj, const char *name,
+                                  Error **errp)
+{
+    /* FIXME: qobject_to_qint mishandles values over INT64_MAX */
+    QmpInputVisitor *qiv = to_qiv(v);
+    QInt *qint = qobject_to_qint(qmp_input_get_object(qiv, name, true));
+
+    if (!qint) {
+        error_setg(errp, QERR_INVALID_PARAMETER_TYPE, name ? name : "null",
+                   "integer");
+        return;
+    }
+
+    *obj = qint_get_int(qint);
+}
+
 static void qmp_input_type_bool(Visitor *v, bool *obj, const char *name,
                                 Error **errp)
 {
@@ -343,6 +359,7 @@ QmpInputVisitor *qmp_input_visitor_new(QObject *obj)
     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;
     v->visitor.type_str = qmp_input_type_str;
     v->visitor.type_number = qmp_input_type_number;
diff --git a/qapi/qmp-output-visitor.c b/qapi/qmp-output-visitor.c
index a13cf91..8a24a00 100644
--- a/qapi/qmp-output-visitor.c
+++ b/qapi/qmp-output-visitor.c
@@ -166,6 +166,14 @@ static void qmp_output_type_int64(Visitor *v, int64_t *obj, const char *name,
     qmp_output_add(qov, name, qint_from_int(*obj));
 }
 
+static void qmp_output_type_uint64(Visitor *v, uint64_t *obj, const char *name,
+                                   Error **errp)
+{
+    /* FIXME: QMP outputs values larger than INT64_MAX as negative */
+    QmpOutputVisitor *qov = to_qov(v);
+    qmp_output_add(qov, name, qint_from_int(*obj));
+}
+
 static void qmp_output_type_bool(Visitor *v, bool *obj, const char *name,
                                  Error **errp)
 {
@@ -243,6 +251,7 @@ QmpOutputVisitor *qmp_output_visitor_new(void)
     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;
     v->visitor.type_str = qmp_output_type_str;
     v->visitor.type_number = qmp_output_type_number;
diff --git a/qapi/string-input-visitor.c b/qapi/string-input-visitor.c
index ffe8cb2..4c23447 100644
--- a/qapi/string-input-visitor.c
+++ b/qapi/string-input-visitor.c
@@ -227,6 +227,20 @@ error:
                "an int64 value or range");
 }
 
+static void parse_type_uint64(Visitor *v, uint64_t *obj, const char *name,
+                              Error **errp)
+{
+    /* FIXME: parse_type_int64 mishandles values over INT64_MAX */
+    int64_t i;
+    Error *err = NULL;
+    parse_type_int64(v, &i, name, &err);
+    if (err) {
+        error_propagate(errp, err);
+    } else {
+        *obj = i;
+    }
+}
+
 static void parse_type_size(Visitor *v, uint64_t *obj, const char *name,
                             Error **errp)
 {
@@ -337,6 +351,7 @@ StringInputVisitor *string_input_visitor_new(const char *str)
 
     v->visitor.type_enum = input_type_enum;
     v->visitor.type_int64 = parse_type_int64;
+    v->visitor.type_uint64 = parse_type_uint64;
     v->visitor.type_size = parse_type_size;
     v->visitor.type_bool = parse_type_bool;
     v->visitor.type_str = parse_type_str;
diff --git a/qapi/string-output-visitor.c b/qapi/string-output-visitor.c
index cf8dfc8..8400c8b 100644
--- a/qapi/string-output-visitor.c
+++ b/qapi/string-output-visitor.c
@@ -198,6 +198,14 @@ static void print_type_int64(Visitor *v, int64_t *obj, const char *name,
     }
 }
 
+static void print_type_uint64(Visitor *v, uint64_t *obj, const char *name,
+                             Error **errp)
+{
+    /* FIXME: print_type_int64 mishandles values over INT64_MAX */
+    int64_t i = *obj;
+    print_type_int64(v, &i, name, errp);
+}
+
 static void print_type_size(Visitor *v, uint64_t *obj, const char *name,
                            Error **errp)
 {
@@ -347,6 +355,7 @@ StringOutputVisitor *string_output_visitor_new(bool human)
     v->human = human;
     v->visitor.type_enum = output_type_enum;
     v->visitor.type_int64 = print_type_int64;
+    v->visitor.type_uint64 = print_type_uint64;
     v->visitor.type_size = print_type_size;
     v->visitor.type_bool = print_type_bool;
     v->visitor.type_str = print_type_str;
