diff --git a/src/reflect/type.go b/src/reflect/type.go
index ec26bef..38b1283 100644
--- a/src/reflect/type.go
+++ b/src/reflect/type.go
@@ -3068,6 +3068,7 @@
 	return t.kind&kindDirectIface == 0
 }
 
+// Note: this type must agree with runtime.bitvector.
 type bitVector struct {
 	n    uint32 // number of bits
 	data []byte
diff --git a/src/reflect/value.go b/src/reflect/value.go
index 8ce495a..c6f24a5 100644
--- a/src/reflect/value.go
+++ b/src/reflect/value.go
@@ -589,6 +589,13 @@
 			// Convert v to type typ if v is assignable to a variable
 			// of type t in the language spec.
 			// See issue 28761.
+			if typ.Kind() == Interface {
+				// We must clear the destination before calling assignTo,
+				// in case assignTo writes (with memory barriers) to the
+				// target location used as scratch space. See issue 39541.
+				*(*uintptr)(addr) = 0
+				*(*uintptr)(add(addr, ptrSize, "typ.size == 2*ptrSize")) = 0
+			}
 			v = v.assignTo("reflect.MakeFunc", typ, addr)
 
 			// We are writing to stack. No write barrier.
@@ -2381,6 +2388,7 @@
 // assignTo returns a value v that can be assigned directly to typ.
 // It panics if v is not assignable to typ.
 // For a conversion to an interface type, target is a suggested scratch space to use.
+// target must be initialized memory (or nil).
 func (v Value) assignTo(context string, dst *rtype, target unsafe.Pointer) Value {
 	if v.flag&flagMethod != 0 {
 		v = makeMethodValue(context, v)
diff --git a/src/runtime/stack.go b/src/runtime/stack.go
index 52e5417..0e930f6 100644
--- a/src/runtime/stack.go
+++ b/src/runtime/stack.go
@@ -556,6 +556,7 @@
 }
 
 // Information from the compiler about the layout of stack frames.
+// Note: this type must agree with reflect.bitVector.
 type bitvector struct {
 	n        int32 // # of bits
 	bytedata *uint8
diff --git a/test/fixedbugs/issue39541.go b/test/fixedbugs/issue39541.go
new file mode 100644
index 0000000..fba5291
--- /dev/null
+++ b/test/fixedbugs/issue39541.go
@@ -0,0 +1,33 @@
+// run
+
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import "reflect"
+
+func sub(args []reflect.Value) []reflect.Value {
+	type A struct {
+		s int
+		t int
+	}
+	return []reflect.Value{reflect.ValueOf(A{1, 2})}
+}
+
+func main() {
+	f := reflect.MakeFunc(reflect.TypeOf((func() interface{})(nil)), sub).Interface().(func() interface{})
+	c := make(chan bool, 100)
+	for i := 0; i < 100; i++ {
+		go func() {
+			for j := 0; j < 10000; j++ {
+				f()
+			}
+			c <- true
+		}()
+	}
+	for i := 0; i < 100; i++ {
+		<-c
+	}
+}