diff --git a/runtime/lua/vim/lsp/util.lua b/runtime/lua/vim/lsp/util.lua
index c759d9e957..ae733b04d6 100644
--- a/runtime/lua/vim/lsp/util.lua
+++ b/runtime/lua/vim/lsp/util.lua
@@ -1547,7 +1547,7 @@ function M._make_floating_popup_size(contents, opts)
     width = 0
     for i, line in ipairs(contents) do
       -- TODO(ashkan) use nvim_strdisplaywidth if/when that is introduced.
-      line_widths[i] = vim.fn.strdisplaywidth(line)
+      line_widths[i] = vim.fn.strdisplaywidth(line:gsub('%z', '\n'))
       width = math.max(line_widths[i], width)
     end
   end
@@ -1576,7 +1576,7 @@ function M._make_floating_popup_size(contents, opts)
       height = 0
       if vim.tbl_isempty(line_widths) then
         for _, line in ipairs(contents) do
-          local line_width = vim.fn.strdisplaywidth(line)
+          local line_width = vim.fn.strdisplaywidth(line:gsub('%z', '\n'))
           height = height + math.ceil(line_width / wrap_at)
         end
       else
diff --git a/test/functional/plugin/lsp_spec.lua b/test/functional/plugin/lsp_spec.lua
index 7d91bd6a0b..2e1a31b89b 100644
--- a/test/functional/plugin/lsp_spec.lua
+++ b/test/functional/plugin/lsp_spec.lua
@@ -2897,6 +2897,18 @@ describe('LSP', function()
     it('calculates size correctly with wrapping', function()
       eq({15,5}, exec_lua[[ return {vim.lsp.util._make_floating_popup_size(contents,{width = 15, wrap_at = 14})} ]])
     end)
+
+    it('handles NUL bytes in text', function()
+      exec_lua([[ contents = {
+        '\000\001\002\003\004\005\006\007\008\009',
+        '\010\011\012\013\014\015\016\017\018\019',
+        '\020\021\022\023\024\025\026\027\028\029',
+      } ]])
+      command('set list listchars=')
+      eq({20,3}, exec_lua[[ return {vim.lsp.util._make_floating_popup_size(contents)} ]])
+      command('set display+=uhex')
+      eq({40,3}, exec_lua[[ return {vim.lsp.util._make_floating_popup_size(contents)} ]])
+    end)
   end)
 
   describe('lsp.util.trim.trim_empty_lines', function()