diff --git a/google/internal/externalaccount/impersonate.go b/google/internal/externalaccount/impersonate.go
index f848bff..1d29c46 100644
--- a/google/internal/externalaccount/impersonate.go
+++ b/google/internal/externalaccount/impersonate.go
@@ -64,7 +64,7 @@ func (its impersonateTokenSource) Token() (*oauth2.Token, error) {
 		return nil, fmt.Errorf("oauth2/google: unable to read body: %v", err)
 	}
 	if c := resp.StatusCode; c < 200 || c > 299 {
-		return nil, fmt.Errorf("oauth2/google: status code %d: %s", c, string(body))
+		return nil, fmt.Errorf("oauth2/google: status code %d: %s", c, body)
 	}
 
 	var accessTokenResp impersonateTokenResponse
diff --git a/google/internal/externalaccount/sts_exchange.go b/google/internal/externalaccount/sts_exchange.go
index ca5f53e..fbb477d 100644
--- a/google/internal/externalaccount/sts_exchange.go
+++ b/google/internal/externalaccount/sts_exchange.go
@@ -66,7 +66,7 @@ func ExchangeToken(ctx context.Context, endpoint string, request *STSTokenExchan
 
 	body, err := ioutil.ReadAll(io.LimitReader(resp.Body, 1<<20))
 	if c := resp.StatusCode; c < 200 || c > 299 {
-		return nil, fmt.Errorf("oauth2/google: status code %d: %s", c, string(body))
+		return nil, fmt.Errorf("oauth2/google: status code %d: %s", c, body)
 	}
 	var stsResp STSTokenExchangeResponse
 	err = json.Unmarshal(body, &stsResp)
diff --git a/google/internal/externalaccount/sts_exchange_test.go b/google/internal/externalaccount/sts_exchange_test.go
index 16c86a3..7f6ce67 100644
--- a/google/internal/externalaccount/sts_exchange_test.go
+++ b/google/internal/externalaccount/sts_exchange_test.go
@@ -97,7 +97,7 @@ func TestExchangeToken_Err(t *testing.T) {
 	headers.Add("Content-Type", "application/x-www-form-urlencoded")
 	_, err := ExchangeToken(context.Background(), ts.URL, &tokenRequest, auth, headers, nil)
 	if err == nil {
-		t.Errorf("Expected handled error; instead got nil.")
+		t.Errorf(" Expected handled error; instead got nil.")
 	}
 }
 
diff --git a/google/internal/externalaccount/urlcredsource.go b/google/internal/externalaccount/urlcredsource.go
index dce704e..91b8f20 100644
--- a/google/internal/externalaccount/urlcredsource.go
+++ b/google/internal/externalaccount/urlcredsource.go
@@ -39,18 +39,18 @@ func (cs urlCredentialSource) subjectToken() (string, error) {
 	}
 	defer resp.Body.Close()
 
-	tokenBytes, err := ioutil.ReadAll(io.LimitReader(resp.Body, 1<<20))
+	respBody, err := ioutil.ReadAll(io.LimitReader(resp.Body, 1<<20))
 	if err != nil {
 		return "", fmt.Errorf("oauth2/google: invalid body in subject token URL query: %v", err)
 	}
 	if c := resp.StatusCode; c < 200 || c > 299 {
-		return "", fmt.Errorf("oauth2/google: status code %d: %s", c, string(tokenBytes))
+		return "", fmt.Errorf("oauth2/google: status code %d: %s", c, respBody)
 	}
 
 	switch cs.Format.Type {
 	case "json":
 		jsonData := make(map[string]interface{})
-		err = json.Unmarshal(tokenBytes, &jsonData)
+		err = json.Unmarshal(respBody, &jsonData)
 		if err != nil {
 			return "", fmt.Errorf("oauth2/google: failed to unmarshal subject token file: %v", err)
 		}
@@ -64,9 +64,9 @@ func (cs urlCredentialSource) subjectToken() (string, error) {
 		}
 		return token, nil
 	case "text":
-		return string(tokenBytes), nil
+		return string(respBody), nil
 	case "":
-		return string(tokenBytes), nil
+		return string(respBody), nil
 	default:
 		return "", errors.New("oauth2/google: invalid credential_source file format type")
 	}
diff --git a/google/internal/externalaccount/urlcredsource_test.go b/google/internal/externalaccount/urlcredsource_test.go
index 1b78e68..6874f11 100644
--- a/google/internal/externalaccount/urlcredsource_test.go
+++ b/google/internal/externalaccount/urlcredsource_test.go
@@ -7,6 +7,7 @@ package externalaccount
 import (
 	"context"
 	"encoding/json"
+	"fmt"
 	"net/http"
 	"net/http/httptest"
 	"testing"
@@ -19,11 +20,18 @@ func TestRetrieveURLSubjectToken_Text(t *testing.T) {
 		if r.Method != "GET" {
 			t.Errorf("Unexpected request method, %v is found", r.Method)
 		}
+		fmt.Println(r.Header)
+		if r.Header.Get("Metadata") != "True" {
+			t.Errorf("Metadata header not properly included.")
+		}
 		w.Write([]byte("testTokenValue"))
 	}))
+	heads := make(map[string]string)
+	heads["Metadata"] = "True"
 	cs := CredentialSource{
 		URL:    ts.URL,
 		Format: format{Type: fileTypeText},
+		Headers: heads,
 	}
 	tfc := testFileConfig
 	tfc.CredentialSource = cs