diff --git a/lib/bdfr_browser/render_utils.ex b/lib/bdfr_browser/render_utils.ex
index 1530acd..08f8bb2 100644
--- a/lib/bdfr_browser/render_utils.ex
+++ b/lib/bdfr_browser/render_utils.ex
@@ -1,13 +1,13 @@
 defmodule BdfrBrowser.RenderUtils do
-  def selftext(txt) do
+  def selftext(txt) when is_binary(txt) do
     Earmark.as_html!(txt)
   end
 
-  def comment(cmt) do
+  def comment(cmt) when is_binary(cmt) do
     Earmark.as_html!(cmt)
   end
 
-  def message(msg) do
+  def message(msg) when is_binary(msg) do
     img_replacement =
       "<p class=\"text-center\"><img src=\"/chat_media/\\1\" class=\"img-fluid\" loading=\"lazy\" /></p>"
 
@@ -17,12 +17,12 @@ defmodule BdfrBrowser.RenderUtils do
     |> Earmark.as_html!()
   end
 
-  def link_to_user(name) when name in ~w([deleted] DELETED), do: name
-  def link_to_user(name), do: "<a href=\"/user/#{name}\">#{name}</a>"
+  def link_to_user(name) when is_binary(name) and name in ~w([deleted] DELETED), do: name
+  def link_to_user(name) when is_binary(name), do: "<a href=\"/user/#{name}\">#{name}</a>"
 
   # Helper
 
-  defp maybe_insert_image(<<"mxc://reddit.com/", filename::binary>> = msg, replacement) do
+  defp maybe_insert_image(<<"mxc://reddit.com/", filename::binary>> = msg, replacement) when is_binary(msg) do
     chat_directory = Application.fetch_env!(:bdfr_browser, :chat_directory)
     img_directory = Path.join([chat_directory, "images"])
     imgs = Path.wildcard("#{img_directory}/#{filename}.*")
@@ -35,5 +35,5 @@ defmodule BdfrBrowser.RenderUtils do
     end
   end
 
-  defp maybe_insert_image(msg, _replacement), do: msg
+  defp maybe_insert_image(msg, _replacement) when is_binary(msg), do: msg
 end