diff --git a/copyparty/__main__.py b/copyparty/__main__.py
index ac06294f..8e79a5fa 100644
--- a/copyparty/__main__.py
+++ b/copyparty/__main__.py
@@ -1735,7 +1735,7 @@ def add_safety(ap):
         ap2.add_argument("--use-bwrap", metavar="TXT", type=u, default="n", help=argparse.SUPPRESS)
 
 
-def add_salt(ap, fk_salt, dk_salt, ah_salt):
+def add_salt(ap, fk_salt, dk_salt, ah_salt, wopi_salt):
     ap2 = ap.add_argument_group("salting options")
     ap2.add_argument("--ah-alg", metavar="ALG", type=u, default="none", help="account-pw hashing algorithm; one of these, best to worst: \033[32margon2 scrypt sha2 none\033[0m (each optionally followed by alg-specific comma-sep. config)")
     ap2.add_argument("--ah-salt", metavar="SALT", type=u, default=ah_salt, help="account-pw salt; ignored if \033[33m--ah-alg\033[0m is none (default)")
@@ -1744,6 +1744,7 @@ def add_salt(ap, fk_salt, dk_salt, ah_salt):
     ap2.add_argument("--fk-salt", metavar="SALT", type=u, default=fk_salt, help="per-file accesskey salt; used to generate unpredictable URLs for hidden files")
     ap2.add_argument("--dk-salt", metavar="SALT", type=u, default=dk_salt, help="per-directory accesskey salt; used to generate unpredictable URLs to share folders with users who only have the 'get' permission")
     ap2.add_argument("--warksalt", metavar="SALT", type=u, default="hunter2", help="up2k file-hash salt; serves no purpose, no reason to change this (but delete all databases if you do)")
+    ap2.add_argument("--wopi-salt", metavar="SALT", type=u, default=wopi_salt, help="WOPI file ID salt; used with \033[33m--wopi\033[0m to generate persistent yet unpredictable WOPI file IDs")
     ap2.add_argument("--show-ah-salt", action="store_true", help="on startup, print the effective value of \033[33m--ah-salt\033[0m (the autogenerated value in $XDG_CONFIG_HOME unless otherwise specified)")
     ap2.add_argument("--show-fk-salt", action="store_true", help="on startup, print the effective value of \033[33m--fk-salt\033[0m (the autogenerated value in $XDG_CONFIG_HOME unless otherwise specified)")
     ap2.add_argument("--show-dk-salt", action="store_true", help="on startup, print the effective value of \033[33m--dk-salt\033[0m (the autogenerated value in $XDG_CONFIG_HOME unless otherwise specified)")
@@ -2076,6 +2077,7 @@ def run_argparse(
     fk_salt = get_salt("fk", 18)
     dk_salt = get_salt("dk", 30)
     ah_salt = get_salt("ah", 18)
+    wopi_salt = get_salt("wopi", 18)
 
     # alpine peaks at 5 threads for some reason,
     # all others scale past that (but try to avoid SMT),
@@ -2112,7 +2114,7 @@ def run_argparse(
     add_opds(ap)
     add_wopi(ap)
     add_safety(ap)
-    add_salt(ap, fk_salt, dk_salt, ah_salt)
+    add_salt(ap, fk_salt, dk_salt, ah_salt, wopi_salt)
     add_optouts(ap)
     add_shutdown(ap)
     add_yolo(ap)
diff --git a/copyparty/httpcli.py b/copyparty/httpcli.py
index a81a9b87..3cd10319 100644
--- a/copyparty/httpcli.py
+++ b/copyparty/httpcli.py
@@ -1649,7 +1649,8 @@ class HttpCli(object):
                 raise Pebkac(500, "too many wopi sessions")
             if not found:
                 atoken = ub64enc(os.urandom(18)).decode("ascii")  #  18 = 144b = 24c
-                file_id = ub64enc(os.urandom(15)).decode("ascii")  # 15 = 120b = 20c
+                zb = (vpath + self.args.wopi_salt).encode("utf-8", "replace")
+                file_id = ub64enc(hashlib.sha512(zb).digest()[:15]).decode("ascii")
                 wopi_files[atoken] = session = {
                     "vp": vpath,
                     "uname": self.uname,