diff --git a/src/reflect/all_test.go b/src/reflect/all_test.go
index 69d5378049..6cc1c9abad 100644
--- a/src/reflect/all_test.go
+++ b/src/reflect/all_test.go
@@ -8001,6 +8001,17 @@ func TestSetIter(t *testing.T) {
 	if got := *y.Interface().(*int); got != b {
 		t.Errorf("pointer incorrect: got %d want %d", got, b)
 	}
+
+	// Make sure we panic assigning from an unexported field.
+	m = ValueOf(struct{ m map[string]int }{data}).Field(0)
+	for iter := m.MapRange(); iter.Next(); {
+		shouldPanic("using value obtained using unexported field", func() {
+			k.SetIterKey(iter)
+		})
+		shouldPanic("using value obtained using unexported field", func() {
+			v.SetIterValue(iter)
+		})
+	}
 }
 
 func TestMethodCallValueCodePtr(t *testing.T) {
diff --git a/src/reflect/value.go b/src/reflect/value.go
index 2589a6dd18..5276af6fd6 100644
--- a/src/reflect/value.go
+++ b/src/reflect/value.go
@@ -1837,7 +1837,8 @@ func (iter *MapIter) Key() Value {
 
 // SetIterKey assigns to v the key of iter's current map entry.
 // It is equivalent to v.Set(iter.Key()), but it avoids allocating a new Value.
-// As in Go, the key must be assignable to v's type.
+// As in Go, the key must be assignable to v's type and
+// must not be derived from an unexported field.
 func (v Value) SetIterKey(iter *MapIter) {
 	if !iter.hiter.initialized() {
 		panic("reflect: Value.SetIterKey called before Next")
@@ -1856,6 +1857,7 @@ func (v Value) SetIterKey(iter *MapIter) {
 	t := (*mapType)(unsafe.Pointer(iter.m.typ))
 	ktype := t.key
 
+	iter.m.mustBeExported() // do not let unexported m leak
 	key := Value{ktype, iterkey, iter.m.flag | flag(ktype.Kind()) | flagIndir}
 	key = key.assignTo("reflect.MapIter.SetKey", v.typ, target)
 	typedmemmove(v.typ, v.ptr, key.ptr)
@@ -1878,7 +1880,8 @@ func (iter *MapIter) Value() Value {
 
 // SetIterValue assigns to v the value of iter's current map entry.
 // It is equivalent to v.Set(iter.Value()), but it avoids allocating a new Value.
-// As in Go, the value must be assignable to v's type.
+// As in Go, the value must be assignable to v's type and
+// must not be derived from an unexported field.
 func (v Value) SetIterValue(iter *MapIter) {
 	if !iter.hiter.initialized() {
 		panic("reflect: Value.SetIterValue called before Next")
@@ -1897,6 +1900,7 @@ func (v Value) SetIterValue(iter *MapIter) {
 	t := (*mapType)(unsafe.Pointer(iter.m.typ))
 	vtype := t.elem
 
+	iter.m.mustBeExported() // do not let unexported m leak
 	elem := Value{vtype, iterelem, iter.m.flag | flag(vtype.Kind()) | flagIndir}
 	elem = elem.assignTo("reflect.MapIter.SetValue", v.typ, target)
 	typedmemmove(v.typ, v.ptr, elem.ptr)
@@ -2218,7 +2222,8 @@ func (v Value) send(x Value, nb bool) (selected bool) {
 
 // Set assigns x to the value v.
 // It panics if CanSet returns false.
-// As in Go, x's value must be assignable to v's type.
+// As in Go, x's value must be assignable to v's type and
+// must not be derived from an unexported field.
 func (v Value) Set(x Value) {
 	v.mustBeAssignable()
 	x.mustBeExported() // do not let unexported x leak