diff --git a/lua/gitsigns/actions.lua b/lua/gitsigns/actions.lua
index 6d96b10..13995eb 100644
--- a/lua/gitsigns/actions.lua
+++ b/lua/gitsigns/actions.lua
@@ -568,9 +568,9 @@ end
 local function insert_hunk_hlmarks(fmt, hunk)
    for _, line in ipairs(fmt) do
       for _, s in ipairs(line) do
-         if s[1] == '<hunk>' then
-            local orig_hl = s[2]
-            s[2] = hlmarks_for_hunk(hunk, orig_hl)
+         local hl = s[2]
+         if s[1] == '<hunk>' and type(hl) == "string" then
+            s[2] = hlmarks_for_hunk(hunk, hl)
          end
       end
    end
@@ -595,17 +595,19 @@ M.preview_hunk = noautocmd(function()
 
    if not hunk then return end
 
-   local lines_spec = lines_format({
+   local lines_fmt = {
       { { 'Hunk <hunk_no> of <num_hunks>', 'Title' } },
       { { '<hunk>', 'Normal' } },
-   }, {
+   }
+
+   insert_hunk_hlmarks(lines_fmt, hunk)
+
+   local lines_spec = lines_format(lines_fmt, {
       hunk_no = index,
       num_hunks = #bcache.hunks,
       hunk = gs_hunks.patch_lines(hunk, vim.bo[cbuf].fileformat),
    })
 
-   insert_hunk_hlmarks(lines_spec, hunk)
-
    popup.create(lines_spec, config.preview_config)
 end)
 
diff --git a/teal/gitsigns/actions.tl b/teal/gitsigns/actions.tl
index 8383f4f..355fb91 100644
--- a/teal/gitsigns/actions.tl
+++ b/teal/gitsigns/actions.tl
@@ -568,9 +568,9 @@ end
 local function insert_hunk_hlmarks(fmt: popup.LinesSpec, hunk: Hunk)
   for _, line in ipairs(fmt) do
     for _, s in ipairs(line) do
-      if s[1] == '<hunk>' then
-        local orig_hl = s[2] as string
-        s[2] = hlmarks_for_hunk(hunk, orig_hl)
+      local hl = s[2]
+      if s[1] == '<hunk>' and hl is string then
+        s[2] = hlmarks_for_hunk(hunk, hl)
       end
     end
   end
@@ -595,17 +595,19 @@ M.preview_hunk = noautocmd(function()
 
   if not hunk then return end
 
-  local lines_spec = lines_format({
+  local lines_fmt = {
     {{'Hunk <hunk_no> of <num_hunks>', 'Title'}},
     {{'<hunk>', 'Normal' }}
-  }, {
+  }
+
+  insert_hunk_hlmarks(lines_fmt, hunk)
+
+  local lines_spec = lines_format(lines_fmt, {
     hunk_no = index,
     num_hunks = #bcache.hunks,
     hunk = gs_hunks.patch_lines(hunk, vim.bo[cbuf].fileformat),
   })
 
-  insert_hunk_hlmarks(lines_spec, hunk)
-
   popup.create(lines_spec, config.preview_config)
 end)
 
diff --git a/types/types.d.tl b/types/types.d.tl
index efe2c68..86a1dd0 100644
--- a/types/types.d.tl
+++ b/types/types.d.tl
@@ -477,6 +477,8 @@ global record vim
     end
   end
   notify: function(string, integer, table)
+  pretty_print: function(any)
+
   split: function(string, string): {string}
   split: function(string, string, boolean): {string}