diff --git a/cache.go b/cache.go
index c5fecae..da5b98a 100644
--- a/cache.go
+++ b/cache.go
@@ -3,7 +3,6 @@ package httpcache
 import (
 	"bufio"
 	"bytes"
-	"crypto/sha256"
 	"errors"
 	"fmt"
 	"io"
@@ -16,6 +15,7 @@ import (
 	"strings"
 	"time"
 
+	"hash/fnv"
 	"github.com/rainycape/vfs"
 )
 
@@ -190,8 +190,8 @@ func (c *Cache) Freshen(res *Resource, keys ...string) error {
 }
 
 func hashKey(key string) string {
-	h := sha256.New()
-	io.WriteString(h, key)
+	h := fnv.New64a()
+	h.Write([]byte(key))
 	return fmt.Sprintf("%x", h.Sum(nil))
 }