diff --git a/cmp/cmpopts/equate.go b/cmp/cmpopts/equate.go
index 62837c9..1dace8b 100644
--- a/cmp/cmpopts/equate.go
+++ b/cmp/cmpopts/equate.go
@@ -6,6 +6,7 @@
 package cmpopts
 
 import (
+	"errors"
 	"math"
 	"reflect"
 	"time"
@@ -136,6 +137,12 @@ func EquateErrors() cmp.Option {
 	return cmp.FilterValues(areConcreteErrors, cmp.Comparer(compareErrors))
 }
 
+func compareErrors(x, y interface{}) bool {
+	xe := x.(error)
+	ye := y.(error)
+	return errors.Is(xe, ye) || errors.Is(ye, xe)
+}
+
 // areConcreteErrors reports whether x and y are types that implement error.
 // The input types are deliberately of the interface{} type rather than the
 // error type so that we can handle situations where the current type is an
diff --git a/cmp/cmpopts/errors_go113.go b/cmp/cmpopts/errors_go113.go
deleted file mode 100644
index 8eb2b84..0000000
--- a/cmp/cmpopts/errors_go113.go
+++ /dev/null
@@ -1,16 +0,0 @@
-// Copyright 2021, 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.
-
-//go:build go1.13
-// +build go1.13
-
-package cmpopts
-
-import "errors"
-
-func compareErrors(x, y interface{}) bool {
-	xe := x.(error)
-	ye := y.(error)
-	return errors.Is(xe, ye) || errors.Is(ye, xe)
-}
diff --git a/go.mod b/go.mod
index b570017..f55cea6 100644
--- a/go.mod
+++ b/go.mod
@@ -1,3 +1,3 @@
 module github.com/google/go-cmp
 
-go 1.11
+go 1.13