diff --git a/lua/git/diff.lua b/lua/git/diff.lua
index dde60da..6374fc6 100644
--- a/lua/git/diff.lua
+++ b/lua/git/diff.lua
@@ -39,11 +39,16 @@ local function attach_index_writer(buf, worktree, path)
                 end
                 vim.b[buf].git_index_mode = mode
             end
+            -- Use the 3-arg form (mode sha path) instead of the comma form
+            -- (mode,sha,path), which doesn't survive paths containing a
+            -- comma.
             local upd = vim.system({
                 "git",
                 "update-index",
                 "--cacheinfo",
-                mode .. "," .. sha .. "," .. path,
+                mode,
+                sha,
+                path,
             }, { cwd = worktree, text = true }):wait()
             if upd.code ~= 0 then
                 log.error("git update-index failed: %s", upd.stderr or "")