diff --git a/src/hex_tarball.erl b/src/hex_tarball.erl
index 7c2d622..9131862 100644
--- a/src/hex_tarball.erl
+++ b/src/hex_tarball.erl
@@ -457,7 +457,7 @@ characters_to_list(Binary) ->
 normalize_metadata(Metadata1) ->
     Metadata2 = maybe_update_with(<<"requirements">>, fun normalize_requirements/1, Metadata1),
     Metadata3 = maybe_update_with(<<"links">>, fun try_into_map/1, Metadata2),
-    Metadata4 = maybe_update_with(<<"extra">>, fun try_into_map/1, Metadata3),
+    Metadata4 = maybe_update_with(<<"extra">>, fun try_into_nested_map/1, Metadata3),
     guess_build_tools(Metadata4).
 
 %% @private
@@ -665,14 +665,29 @@ try_into_map(List) ->
 
 %% @private
 try_into_map(Fun, Input) ->
-    case
-        is_list(Input) andalso
-            lists:all(fun(E) -> is_tuple(E) andalso (tuple_size(E) == 2) end, Input)
-    of
+    case has_map_shape(Input) of
         true -> maps:from_list(lists:map(Fun, Input));
         false -> Input
     end.
 
+%% @private
+try_into_nested_map(List) ->
+    try_into_nested_map(fun(X) -> X end, List).
+
+%% @private
+try_into_nested_map(Fun, Input) ->
+    case has_map_shape(Input) of
+        true -> maps:from_list(lists:map(fun({Key, Value}) ->
+          Fun({Key, try_into_nested_map(Fun, Value)})
+        end, Input));
+        false -> Input
+    end.
+
+%% @private
+has_map_shape(Input) ->
+    is_list(Input) andalso
+        lists:all(fun(E) -> is_tuple(E) andalso (tuple_size(E) == 2) end, Input).
+
 %% @private
 encode_base16(Binary) ->
     <<X:256/big-unsigned-integer>> = Binary,
diff --git a/test/hex_tarball_SUITE.erl b/test/hex_tarball_SUITE.erl
index 9b1aa8c..5f7f398 100644
--- a/test/hex_tarball_SUITE.erl
+++ b/test/hex_tarball_SUITE.erl
@@ -57,17 +57,19 @@ memory_test(_Config) ->
         <<"name">> => <<"foo">>,
         <<"version">> => <<"1.0.0">>,
         <<"maintainers">> => [<<"José">>],
-        <<"build_tool">> => <<"rebar3">>
+        <<"build_tool">> => <<"rebar3">>,
+        <<"extra">> => [{<<"foo">>, [{<<"bar">>, <<"baz">>}]}]
     },
     Contents = [{"src/foo.erl", <<"-module(foo).">>}],
     {ok, #{tarball := Tarball, inner_checksum := InnerChecksum, outer_checksum := OuterChecksum}} = hex_tarball:create(
         Metadata, Contents
     ),
+    Metadata1 = maps:put(<<"extra">>, #{<<"foo">> => #{<<"bar">> => <<"baz">>}}, Metadata),
     {ok, #{
         inner_checksum := InnerChecksum,
         outer_checksum := OuterChecksum,
         contents := Contents,
-        metadata := Metadata
+        metadata := Metadata1
     }} = hex_tarball:unpack(Tarball, memory),
     ok.