diff --git a/src/bits.erl b/src/bits.erl
index 4988ab3..cb3b2a7 100644
--- a/src/bits.erl
+++ b/src/bits.erl
@@ -15,7 +15,7 @@
 -module(bits).
 
 -export([reverse/1, duplicate/2, append/1, bitlist/1, bitstring/1, stringbits/1]).
--compile(export_all).
+% export_all removed to avoid warnings; module already exports explicit API.
 
 reverse(Bin) ->
 	reverse(Bin, <<>>).
diff --git a/src/qrcode_demo.erl b/src/qrcode_demo.erl
index aa27174..5522629 100644
--- a/src/qrcode_demo.erl
+++ b/src/qrcode_demo.erl
@@ -41,7 +41,7 @@
 
 -include("qrcode.hrl").
 
--compile(export_all).
+% export_all removed to avoid warnings; demo module is not part of the public API.
 
 -define(TTY(Term), io:format(user, "[~p] ~p~n", [?MODULE, Term])).
 -define(PERIOD, 30).
@@ -108,7 +108,7 @@ totp(Key, Period) ->
 %% RFC-4226 "HOTP: An HMAC-Based One-Time Password Algorithm"
 %% @ref <http://tools.ietf.org/html/rfc4226>
 hotp(Key, Count) when is_binary(Key), is_integer(Count) ->
-	HS = crypto:hmac(sha, Key, <<Count:64>>),
+	HS = crypto:mac(hmac, sha, Key, <<Count:64>>),
 	<<_:19/binary, _:4, Offset:4>> = HS,
 	<<_:Offset/binary, _:1, P:31, _/binary>> = HS,
 	HOTP = integer_to_list(P rem 1000000),