diff --git a/examples/README.md b/examples/README.md
index 0109c17..f2ec29c 100644
--- a/examples/README.md
+++ b/examples/README.md
@@ -75,7 +75,7 @@
 
 type uppercaseResponse struct {
 	V   string `json:"v"`
-	Err error  `json:"err"`
+	Err string `json:"err"` // errors don't define JSON marshaling
 }
 
 type countRequest struct {
@@ -109,7 +109,7 @@
 	return func(ctx context.Context, request interface{}) (interface{}, error) {
 		req := request.(uppercaseRequest)
 		v, err := svc.Uppercase(req.S)
-		return uppercaseResponse{v, err}, nil
+		return uppercaseResponse{v, err.Error()}, nil
 	}
 }
 
@@ -483,7 +483,10 @@
 		return "", err
 	}
 	resp := response.(uppercaseResponse)
-	return resp.V, resp.Err
+	if resp.Err != "" {
+		return resp.V, errors.New(resp.Err)
+	}
+	return resp.V, nil
 }
 ```
 
diff --git a/examples/stringsvc1/main.go b/examples/stringsvc1/main.go
index e4f5e4e..ea4e5b8 100644
--- a/examples/stringsvc1/main.go
+++ b/examples/stringsvc1/main.go
@@ -59,7 +59,7 @@
 	return func(ctx context.Context, request interface{}) (interface{}, error) {
 		req := request.(uppercaseRequest)
 		v, err := svc.Uppercase(req.S)
-		return uppercaseResponse{v, err}, nil
+		return uppercaseResponse{v, err.Error()}, nil
 	}
 }
 
@@ -97,7 +97,7 @@
 
 type uppercaseResponse struct {
 	V   string `json:"v"`
-	Err error  `json:"err"`
+	Err string `json:"err"` // errors don't define JSON marshaling
 }
 
 type countRequest struct {
diff --git a/examples/stringsvc2/transport.go b/examples/stringsvc2/transport.go
index 8968a13..080cf0d 100644
--- a/examples/stringsvc2/transport.go
+++ b/examples/stringsvc2/transport.go
@@ -13,7 +13,7 @@
 	return func(ctx context.Context, request interface{}) (interface{}, error) {
 		req := request.(uppercaseRequest)
 		v, err := svc.Uppercase(req.S)
-		return uppercaseResponse{v, err}, nil
+		return uppercaseResponse{v, err.Error()}, nil
 	}
 }
 
@@ -51,7 +51,7 @@
 
 type uppercaseResponse struct {
 	V   string `json:"v"`
-	Err error  `json:"err"`
+	Err string `json:"err"`
 }
 
 type countRequest struct {
diff --git a/examples/stringsvc3/proxying.go b/examples/stringsvc3/proxying.go
index b37bb5d..6a10afd 100644
--- a/examples/stringsvc3/proxying.go
+++ b/examples/stringsvc3/proxying.go
@@ -1,6 +1,7 @@
 package main
 
 import (
+	"errors"
 	"fmt"
 	"net/http"
 	"net/url"
@@ -57,7 +58,10 @@
 	}
 
 	resp := response.(uppercaseResponse)
-	return resp.V, resp.Err
+	if resp.Err != "" {
+		return resp.V, errors.New(resp.Err)
+	}
+	return resp.V, nil
 }
 
 func factory(ctx context.Context, qps int) loadbalancer.Factory {
diff --git a/examples/stringsvc3/transport.go b/examples/stringsvc3/transport.go
index 7e5e8d5..cb5c4e9 100644
--- a/examples/stringsvc3/transport.go
+++ b/examples/stringsvc3/transport.go
@@ -15,7 +15,7 @@
 	return func(ctx context.Context, request interface{}) (interface{}, error) {
 		req := request.(uppercaseRequest)
 		v, err := svc.Uppercase(req.S)
-		return uppercaseResponse{v, err}, nil
+		return uppercaseResponse{v, err.Error()}, nil
 	}
 }
 
@@ -70,7 +70,7 @@
 
 type uppercaseResponse struct {
 	V   string `json:"v"`
-	Err error  `json:"err"`
+	Err string `json:"err"`
 }
 
 type countRequest struct {