diff --git a/rebar.config b/rebar.config
index 38b6088..15ffea3 100644
--- a/rebar.config
+++ b/rebar.config
@@ -28,6 +28,7 @@
 {dialyzer, [ {warnings, [ no_return
                         , unmatched_returns
                         , error_handling
+                        , underspecs
                         ]}
            , {plt_apps, top_level_deps}
            , {plt_extra_apps, [tools, syntax_tools]}
diff --git a/src/ktn_code.erl b/src/ktn_code.erl
index 09b1de2..b95aaea 100644
--- a/src/ktn_code.erl
+++ b/src/ktn_code.erl
@@ -250,7 +250,7 @@ to_str(Arg) when is_list(Arg) ->
 %%% Internal
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
--spec source_encoding(binary() | list()) -> latin1 | utf8.
+-spec source_encoding(binary()) -> latin1 | utf8.
 source_encoding(Source) ->
     Re = ".*\n?.*(coding *[:=] *(?<encoding>[-a-zA-Z0-9]+))",
     ReOpts = [firstline, {capture, all_names, list}],
@@ -836,7 +836,7 @@ to_map(Parsed) when is_tuple(Parsed) ->
 to_map(Parsed) ->
     throw({unexpected_abstract_form, Parsed}).
 
--spec macro_name(any()) -> string().
+-spec macro_name(erl_syntax:syntaxTree()) -> string().
 macro_name(Name) ->
   case erl_syntax:type(Name) of
     atom ->
@@ -855,7 +855,7 @@ macro_name(Name) ->
 %%      NOTE: Copied from ktn_lists not to bring the whole erlang-katana
 %%            repo as a dependency here
 %% @end
--spec split_when(fun(), list()) -> list().
+-spec split_when(fun((T) -> boolean()), [T]) -> [[T]].
 split_when(When, List) ->
     split_when(When, List, [[]]).
 
diff --git a/src/ktn_io_string.erl b/src/ktn_io_string.erl
index 7689301..be1a2f9 100644
--- a/src/ktn_io_string.erl
+++ b/src/ktn_io_string.erl
@@ -112,7 +112,7 @@ do_get_line("\r" ++ RestStr, Result) ->
 do_get_line([Ch | RestStr], Result) ->
     do_get_line(RestStr, [Result, Ch]).
 
--spec get_until(module(), atom(), list(), term()) ->
+-spec get_until(module(), atom(), list(), eof | string()) ->
     {term(), string()}.
 get_until(Module, Function, XArgs, Str) ->
     apply_get_until(Module, Function, [], Str, XArgs).