diff --git a/errors/errors.go b/errors/errors.go
index b373c95fb5f9a968459cc61f68cd345b78404eb6..0da300acf420d24ff7185ef35eb7ba5ac62d7f3a 100644
--- a/errors/errors.go
+++ b/errors/errors.go
@@ -1,6 +1,7 @@
 package errors
 
 import (
+	"errors"
 	"fmt"
 
 	"github.com/vektah/gqlparser/v2/gqlerror"
@@ -28,6 +29,24 @@ // Sets the field name that caused the error
 func Field(err *gqlerror.Error, field string) *gqlerror.Error {
 	err.Extensions["field"] = field
 	return err
+}
+
+// Returns true if the first GraphQL error has the same error code as the
+// reference error. This should be used, for example, to test an error from
+// client.Do against an error initialized by this module (e.g.
+// ErrAccessDenied). These errors do not work with the Go standard library's
+// errors.Is function, nor with ==, thus this function.
+func Is(err error, ref *gqlerror.Error) bool {
+	var gqlerr *gqlerror.Error
+	if !errors.As(err, &gqlerr) {
+		return false
+	}
+	if code, ok := gqlerr.Extensions["code"]; ok {
+		if refCode, ok := ref.Extensions["code"]; ok {
+			return code == refCode
+		}
+	}
+	return false
 }
 
 // Error codes as string constants