diff --git a/fileserver/fileop.go b/fileserver/fileop.go
index e47b30ed..e8013d47 100644
--- a/fileserver/fileop.go
+++ b/fileserver/fileop.go
@@ -643,10 +643,6 @@ func doBlock(rsp http.ResponseWriter, r *http.Request, repo *repomgr.Repo, fileI
 }
 
 func accessZipCB(rsp http.ResponseWriter, r *http.Request) *appError {
-	if seahubPK == "" {
-		err := fmt.Errorf("no seahub private key is configured")
-		return &appError{err, "", http.StatusNotFound}
-	}
 	parts := strings.Split(r.URL.Path[1:], "/")
 	if len(parts) != 2 {
 		msg := "Invalid URL"
@@ -3570,10 +3566,6 @@ func accessLinkCB(rsp http.ResponseWriter, r *http.Request) *appError {
 	fileName := filepath.Base(filePath)
 	op := "download-link"
 
-	if _, ok := r.Header["If-Modified-Since"]; ok {
-		return &appError{nil, "", http.StatusNotModified}
-	}
-
 	ranges := r.Header["Range"]
 	byteRanges := strings.Join(ranges, "")
 
@@ -3591,13 +3583,14 @@ func accessLinkCB(rsp http.ResponseWriter, r *http.Request) *appError {
 		return &appError{nil, msg, http.StatusBadRequest}
 	}
 
+	// Check for file changes by comparing the ETag in the If-None-Match header with the file ID. Set no-cache to allow clients to validate file changes before using the cache.
 	etag := r.Header.Get("If-None-Match")
 	if etag == fileID {
 		return &appError{nil, "", http.StatusNotModified}
 	}
 
 	rsp.Header().Set("ETag", fileID)
-	rsp.Header().Set("Cache-Control", "no-chche")
+	rsp.Header().Set("Cache-Control", "no-cache")
 
 	var cryptKey *seafileCrypt
 	if repo.IsEncrypted {
diff --git a/server/access-file.c b/server/access-file.c
index ce2e68cb..b36a2c4a 100644
--- a/server/access-file.c
+++ b/server/access-file.c
@@ -1119,6 +1119,15 @@ set_etag (evhtp_request_t *req,
     evhtp_kvs_add_kv (req->headers_out, kv);
 }
 
+static void
+set_no_cache (evhtp_request_t *req)
+{
+    evhtp_kv_t *kv;
+
+    kv = evhtp_kv_new ("Cache-Control", "no-cache", 1, 1);
+    evhtp_kvs_add_kv (req->headers_out, kv);
+}
+
 static gboolean
 can_use_cached_content (evhtp_request_t *req)
 {
@@ -1720,6 +1729,7 @@ access_link_cb(evhtp_request_t *req, void *arg)
         goto out;
     }
     set_etag (req, file_id);
+    set_no_cache (req);
 
     byte_ranges = evhtp_kv_find (req->headers_in, "Range");
 
@@ -1772,6 +1782,7 @@ access_link_cb(evhtp_request_t *req, void *arg)
     }
 }
 
+/*
 static GList *
 json_to_dirent_list (SeafRepo *repo, const char *parent_dir, const char *dirents)
 {
@@ -1882,6 +1893,7 @@ get_form_field (const char *body_str, const char *field_name)
     g_free (value);
     return result;
 }
+*/
 
 /*
 static void