diff --git a/lib/elixir/lib/uri.ex b/lib/elixir/lib/uri.ex
index c05d8c94ba9..9acb61dda85 100644
--- a/lib/elixir/lib/uri.ex
+++ b/lib/elixir/lib/uri.ex
@@ -907,7 +907,7 @@ defmodule URI do
     %{rel | path: remove_dot_segments_from_path(rel.path)}
   end
 
-  def merge(base, %URI{host: host} = rel) when host != nil do
+  def merge(%URI{} = base, %URI{host: host} = rel) when host != nil do
     %{rel | scheme: base.scheme, path: remove_dot_segments_from_path(rel.path)}
   end
 
diff --git a/lib/elixir/test/elixir/uri_test.exs b/lib/elixir/test/elixir/uri_test.exs
index 8772ec97d3c..e627b0f84a5 100644
--- a/lib/elixir/test/elixir/uri_test.exs
+++ b/lib/elixir/test/elixir/uri_test.exs
@@ -387,6 +387,9 @@ defmodule URITest do
     assert URI.merge("http://google.com/foo", "//example.com/baz")
            |> to_string == "http://example.com/baz"
 
+    assert URI.merge("http://google.com/foo", URI.new!("//example.com/baz"))
+           |> to_string == "http://example.com/baz"
+
     assert URI.merge("http://google.com/foo", "//example.com/.././bar/../../../baz")
            |> to_string == "http://example.com/baz"