diff --git a/httpcache.go b/httpcache.go
index fa6d9b9..1e560cc 100644
--- a/httpcache.go
+++ b/httpcache.go
@@ -242,7 +242,11 @@ func (t *Transport) RoundTrip(req *http.Request) (resp *http.Response, err error
 			if t.EnableETagPair {
 				if etag := resp.Header.Get("etag"); etag != "" {
 					resp.Header.Set(XETag1, etag)
-					resp.Header.Set(XETag2, cachedXEtag)
+					etag2 := cachedXEtag
+					if etag2 == "" {
+						etag2 = etag
+					}
+					resp.Header.Set(XETag2, etag2)
 				} else {
 					etagHash = md5.New()
 					r = struct {
@@ -261,8 +265,11 @@ func (t *Transport) RoundTrip(req *http.Request) (resp *http.Response, err error
 					if etagHash != nil {
 						md5Str := hex.EncodeToString(etagHash.Sum(nil))
 						resp.Header.Set(XETag1, md5Str)
-						resp.Header.Set(XETag2, cachedXEtag)
-
+						etag2 := cachedXEtag
+						if etag2 == "" {
+							etag2 = md5Str
+						}
+						resp.Header.Set(XETag2, etag2)
 					}
 					resp := *resp
 					resp.Body = io.NopCloser(r)
diff --git a/httpcache_test.go b/httpcache_test.go
index 5d528e3..491dccc 100644
--- a/httpcache_test.go
+++ b/httpcache_test.go
@@ -224,7 +224,7 @@ func TestEnableETagPair(t *testing.T) {
 		_, resp := doMethod(t, "GET", "/etag", nil)
 		c.Assert(resp.StatusCode, qt.Equals, http.StatusOK)
 		c.Assert(resp.Header.Get(XETag1), qt.Equals, "124567")
-		c.Assert(resp.Header.Get(XETag2), qt.Equals, "")
+		c.Assert(resp.Header.Get(XETag2), qt.Equals, "124567")
 	}
 	{
 		_, resp := doMethod(t, "GET", "/etag", nil)
@@ -238,7 +238,7 @@ func TestEnableETagPair(t *testing.T) {
 		_, resp := doMethod(t, "GET", "/helloheaderasbody", map[string]string{"Hello": "world1"})
 		c.Assert(resp.StatusCode, qt.Equals, http.StatusOK)
 		c.Assert(resp.Header.Get(XETag1), qt.Equals, "48b21a691481958c34cc165011bdb9bc")
-		c.Assert(resp.Header.Get(XETag2), qt.Equals, "")
+		c.Assert(resp.Header.Get(XETag2), qt.Equals, "48b21a691481958c34cc165011bdb9bc")
 	}
 	{
 		_, resp := doMethod(t, "GET", "/helloheaderasbody", map[string]string{"Hello": "world2"})