diff --git a/lib/ex_doc/formatter/epub.ex b/lib/ex_doc/formatter/epub.ex
index 0f9136198..94281d99e 100644
--- a/lib/ex_doc/formatter/epub.ex
+++ b/lib/ex_doc/formatter/epub.ex
@@ -76,11 +76,10 @@ defmodule ExDoc.Formatter.EPUB do
 
   defp generate_content(config, nodes, uuid, datetime, static_files) do
     static_files =
-      static_files
-      |> Enum.filter(fn name ->
-        String.contains?(name, "OEBPS") and config.output |> Path.join(name) |> File.regular?()
-      end)
-      |> Enum.map(&Path.relative_to(&1, "OEBPS"))
+      for name <- static_files,
+          String.contains?(name, "OEBPS"),
+          media_type = Templates.media_type(Path.extname(name)),
+          do: {Path.relative_to(name, "OEBPS"), media_type}
 
     content = Templates.content_template(config, nodes, uuid, datetime, static_files)
     File.write("#{config.output}/OEBPS/content.opf", content)
diff --git a/lib/ex_doc/formatter/epub/templates.ex b/lib/ex_doc/formatter/epub/templates.ex
index 93facbfeb..7fd10e2f3 100644
--- a/lib/ex_doc/formatter/epub/templates.ex
+++ b/lib/ex_doc/formatter/epub/templates.ex
@@ -129,11 +129,10 @@ defmodule ExDoc.Formatter.EPUB.Templates do
   |> Enum.each(fn line ->
     [extension, media] = String.split(line, ",")
 
-    defp media_type("." <> unquote(extension)) do
+    def media_type("." <> unquote(extension)) do
       unquote(media)
     end
   end)
 
-  defp media_type(arg),
-    do: raise("asset with extension #{inspect(arg)} is not supported by EPUB format")
+  def media_type(_arg), do: nil
 end
diff --git a/lib/ex_doc/formatter/epub/templates/content_template.eex b/lib/ex_doc/formatter/epub/templates/content_template.eex
index de22444f2..ed7b01939 100644
--- a/lib/ex_doc/formatter/epub/templates/content_template.eex
+++ b/lib/ex_doc/formatter/epub/templates/content_template.eex
@@ -23,14 +23,14 @@
     <%= for filter <- [:modules, :tasks], node <- nodes[filter] do %>
       <item id="<%= URI.encode node.id %>" href="<%= URI.encode node.id %>.xhtml" media-type="application/xhtml+xml" properties="scripted"/>
     <% end %>
-    <%= for static_file <- static_files do %>
-      <item id="<%= static_file_to_id(static_file) %>" href="<%= static_file %>" media-type="<%= media_type(Path.extname(static_file)) %>"/>
+    <%= for {static_file, media_type} <- static_files do %>
+      <item id="<%= static_file_to_id(static_file) %>" href="<%= static_file %>" media-type="<%= media_type %>"/>
     <% end %>
     <%= if config.cover do %>
-      <item id="cover-image" href="assets/cover<%= Path.extname(config.cover) %>" media-type="<%= media_type(Path.extname(config.cover))%>"/>
+      <item id="cover-image" href="assets/cover<%= Path.extname(config.cover) %>" media-type="<%= media_type(Path.extname(config.cover)) %>"/>
     <% end %>
     <%= if config.logo do %>
-      <item id="logo" href="assets/logo<%= Path.extname(config.logo) %>" media-type="<%= media_type(Path.extname(config.logo))%>"/>
+      <item id="logo" href="assets/logo<%= Path.extname(config.logo) %>" media-type="<%= media_type(Path.extname(config.logo)) %>"/>
     <% end %>
   </manifest>
   <spine>
diff --git a/test/ex_doc/formatter/epub_test.exs b/test/ex_doc/formatter/epub_test.exs
index 2bfdc3845..3f6c6e81d 100644
--- a/test/ex_doc/formatter/epub_test.exs
+++ b/test/ex_doc/formatter/epub_test.exs
@@ -67,19 +67,6 @@ defmodule ExDoc.Formatter.EPUBTest do
     assert content =~ ~r{<dc:creator id="author2">Jane Doe</dc:creator>}
   end
 
-  test "raises when assets are invalid", context do
-    File.mkdir_p!("test/tmp/epub_assets/hello")
-    File.touch!("test/tmp/epub_assets/hello/world.pdf")
-
-    assert_raise(
-      RuntimeError,
-      ~s{asset with extension ".pdf" is not supported by EPUB format},
-      fn -> generate_docs(doc_config(context, assets: %{"test/tmp/epub_assets" => "assets"})) end
-    )
-  after
-    File.rm_rf!("test/tmp/epub_assets")
-  end
-
   test "generates an EPUB file in the default directory", %{tmp_dir: tmp_dir} = context do
     generate_docs(doc_config(context))
     assert File.regular?(tmp_dir <> "/epub/#{doc_config(context)[:project]}.epub")
@@ -232,6 +219,7 @@ defmodule ExDoc.Formatter.EPUBTest do
   test "assets required by the user end up in the right place", %{tmp_dir: tmp_dir} = context do
     File.mkdir_p!("test/tmp/epub_assets/hello")
     File.touch!("test/tmp/epub_assets/hello/world.png")
+    File.touch!("test/tmp/epub_assets/hello/world.pdf")
 
     generate_docs_and_unzip(
       context,
@@ -243,6 +231,7 @@ defmodule ExDoc.Formatter.EPUBTest do
     )
 
     assert File.regular?(tmp_dir <> "/epub/OEBPS/assets/hello/world.png")
+    assert File.regular?(tmp_dir <> "/epub/OEBPS/assets/hello/world.pdf")
     assert File.regular?(tmp_dir <> "/epub/OEBPS/assets/logo.png")
     assert File.regular?(tmp_dir <> "/epub/OEBPS/assets/cover.png")
   after