diff --git a/lib/jose/poison/lexical_encoder.ex b/lib/jose/poison/lexical_encoder.ex
index ede8f84..c3cbd52 100644
--- a/lib/jose/poison/lexical_encoder.ex
+++ b/lib/jose/poison/lexical_encoder.ex
@@ -149,7 +149,7 @@ if Code.ensure_loaded?(Poison) do
 
     defp escape("", _), do: []
 
-    for {char, seq} <- Enum.zip('"\\\n\t\r\f\b', '"\\ntrfb') do
+    for {char, seq} <- Enum.zip(~c"\"\\\n\t\r\f\b", ~c"\"\\ntrfb") do
       defp escape(<<unquote(char)>> <> rest, mode) do
         [unquote("\\" <> <<seq>>) | escape(rest, mode)]
       end
@@ -196,7 +196,7 @@ if Code.ensure_loaded?(Poison) do
     end
 
     defp chunk_size(<<char>> <> _, _mode, acc)
-         when char <= 0x1F or char in '"\\' do
+         when char <= 0x1F or char in ~c"\"\\" do
       acc
     end
 
diff --git a/mix.lock b/mix.lock
index 530381f..986913b 100644
--- a/mix.lock
+++ b/mix.lock
@@ -1,17 +1,17 @@
 %{
   "earmark": {:hex, :earmark, "1.4.27", "b413b0379043df51475a9b22ce344e8a58a117516c735b8871e6cdd5ed0f0153", [:mix], [{:earmark_parser, "~> 1.4.26", [hex: :earmark_parser, repo: "hexpm", optional: false]}], "hexpm", "579ebe2eaf4c7e040815a73a268036bcd96e6aab8ad2b1fcd979aaeb1ea47e15"},
-  "earmark_parser": {:hex, :earmark_parser, "1.4.26", "f4291134583f373c7d8755566122908eb9662df4c4b63caa66a0eabe06569b0a", [:mix], [], "hexpm", "48d460899f8a0c52c5470676611c01f64f3337bad0b26ddab43648428d94aabc"},
-  "ex_doc": {:hex, :ex_doc, "0.28.5", "3e52a6d2130ce74d096859e477b97080c156d0926701c13870a4e1f752363279", [:mix], [{:earmark_parser, "~> 1.4.19", [hex: :earmark_parser, repo: "hexpm", optional: false]}, {:makeup_elixir, "~> 0.14", [hex: :makeup_elixir, repo: "hexpm", optional: false]}, {:makeup_erlang, "~> 0.1", [hex: :makeup_erlang, repo: "hexpm", optional: false]}], "hexpm", "d2c4b07133113e9aa3e9ba27efb9088ba900e9e51caa383919676afdf09ab181"},
+  "earmark_parser": {:hex, :earmark_parser, "1.4.33", "3c3fd9673bb5dcc9edc28dd90f50c87ce506d1f71b70e3de69aa8154bc695d44", [:mix], [], "hexpm", "2d526833729b59b9fdb85785078697c72ac5e5066350663e5be6a1182da61b8f"},
+  "ex_doc": {:hex, :ex_doc, "0.30.3", "bfca4d340e3b95f2eb26e72e4890da83e2b3a5c5b0e52607333bf5017284b063", [:mix], [{:earmark_parser, "~> 1.4.31", [hex: :earmark_parser, repo: "hexpm", optional: false]}, {:makeup_elixir, "~> 0.14", [hex: :makeup_elixir, repo: "hexpm", optional: false]}, {:makeup_erlang, "~> 0.1", [hex: :makeup_erlang, repo: "hexpm", optional: false]}], "hexpm", "fbc8702046c1d25edf79de376297e608ac78cdc3a29f075484773ad1718918b6"},
   "jason": {:hex, :jason, "1.4.0", "e855647bc964a44e2f67df589ccf49105ae039d4179db7f6271dfd3843dc27e6", [:mix], [{:decimal, "~> 1.0 or ~> 2.0", [hex: :decimal, repo: "hexpm", optional: true]}], "hexpm", "79a3791085b2a0f743ca04cec0f7be26443738779d09302e01318f97bdb82121"},
-  "jsone": {:hex, :jsone, "1.7.0", "1e3bd7d5dd44bb2eb0797dddea1cbf2ddab8d9f29e499a467ca171c23f5984ea", [:rebar3], [], "hexpm", "a3a33712ee6bc8be10cfa21c7c425a299de4c5a8533f9f931e577a6d0e8f5dbd"},
+  "jsone": {:hex, :jsone, "1.8.0", "347ff1fa700e182e1f9c5012fa6d737b12c854313b9ae6954ca75d3987d6c06d", [:rebar3], [], "hexpm", "08560b78624a12e0b5e7ec0271ec8ca38ef51f63d84d84843473e14d9b12618c"},
   "jsx": {:hex, :jsx, "3.1.0", "d12516baa0bb23a59bb35dccaf02a1bd08243fcbb9efe24f2d9d056ccff71268", [:rebar3], [], "hexpm", "0c5cc8fdc11b53cc25cf65ac6705ad39e54ecc56d1c22e4adb8f5a53fb9427f3"},
   "libdecaf": {:hex, :libdecaf, "2.1.1", "2d2716c1c2aee870d15fbf150dca67210e2a62f11f9126f59019a5ef79f63ad3", [:rebar3], [], "hexpm", "dee36dc9a73cc2384b0f9a53ce7f76c29a1344f28c459678add231cb8a2c4c61"},
   "libsodium": {:hex, :libsodium, "2.0.1", "9bebad374e1b312f620ee6b28a69670b4ba1011b365f91be9271b02f5383570d", [:rebar3], [], "hexpm", "c189198acddc101f9a9f2b94bf29a1132119a982c3738a4679fc5d411f10b58b"},
   "makeup": {:hex, :makeup, "1.1.0", "6b67c8bc2882a6b6a445859952a602afc1a41c2e08379ca057c0f525366fc3ca", [:mix], [{:nimble_parsec, "~> 1.2.2 or ~> 1.3", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm", "0a45ed501f4a8897f580eabf99a2e5234ea3e75a4373c8a52824f6e873be57a6"},
-  "makeup_elixir": {:hex, :makeup_elixir, "0.16.0", "f8c570a0d33f8039513fbccaf7108c5d750f47d8defd44088371191b76492b0b", [:mix], [{:makeup, "~> 1.0", [hex: :makeup, repo: "hexpm", optional: false]}, {:nimble_parsec, "~> 1.2.3", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm", "28b2cbdc13960a46ae9a8858c4bebdec3c9a6d7b4b9e7f4ed1502f8159f338e7"},
-  "makeup_erlang": {:hex, :makeup_erlang, "0.1.1", "3fcb7f09eb9d98dc4d208f49cc955a34218fc41ff6b84df7c75b3e6e533cc65f", [:mix], [{:makeup, "~> 1.0", [hex: :makeup, repo: "hexpm", optional: false]}], "hexpm", "174d0809e98a4ef0b3309256cbf97101c6ec01c4ab0b23e926a9e17df2077cbb"},
-  "nimble_parsec": {:hex, :nimble_parsec, "1.2.3", "244836e6e3f1200c7f30cb56733fd808744eca61fd182f731eac4af635cc6d0b", [:mix], [], "hexpm", "c8d789e39b9131acf7b99291e93dae60ab48ef14a7ee9d58c6964f59efb570b0"},
+  "makeup_elixir": {:hex, :makeup_elixir, "0.16.1", "cc9e3ca312f1cfeccc572b37a09980287e243648108384b97ff2b76e505c3555", [:mix], [{:makeup, "~> 1.0", [hex: :makeup, repo: "hexpm", optional: false]}, {:nimble_parsec, "~> 1.2.3 or ~> 1.3", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm", "e127a341ad1b209bd80f7bd1620a15693a9908ed780c3b763bccf7d200c767c6"},
+  "makeup_erlang": {:hex, :makeup_erlang, "0.1.2", "ad87296a092a46e03b7e9b0be7631ddcf64c790fa68a9ef5323b6cbb36affc72", [:mix], [{:makeup, "~> 1.0", [hex: :makeup, repo: "hexpm", optional: false]}], "hexpm", "f3f5a1ca93ce6e092d92b6d9c049bcda58a3b617a8d888f8e7231c85630e8108"},
+  "nimble_parsec": {:hex, :nimble_parsec, "1.3.1", "2c54013ecf170e249e9291ed0a62e5832f70a476c61da16f6aac6dca0189f2af", [:mix], [], "hexpm", "2682e3c0b2eb58d90c6375fc0cc30bc7be06f365bf72608804fb9cffa5e1b167"},
   "ojson": {:hex, :ojson, "1.0.0", "fd28614eadaec00a15cdb2f53f29d8717a812a508ddb80d202f2f2e2aaeabbcc", [:mix, :rebar3], [], "hexpm", "125088e64d95704194dc8b4b5095502363e0ca870b72712f61929499d3c48d00"},
   "poison": {:hex, :poison, "5.0.0", "d2b54589ab4157bbb82ec2050757779bfed724463a544b6e20d79855a9e43b24", [:mix], [{:decimal, "~> 2.0", [hex: :decimal, repo: "hexpm", optional: true]}], "hexpm", "11dc6117c501b80c62a7594f941d043982a1bd05a1184280c0d9166eb4d8d3fc"},
-  "thoas": {:hex, :thoas, "0.4.0", "86a72ccdc5ec388a13f9f843bcd6c1076640233b95440e47ffb8e3c0dbdb5a17", [:rebar3], [], "hexpm", "442296847aca11db8d25180693d7ca3073d6d7179f66952f07b16415306513b6"},
+  "thoas": {:hex, :thoas, "1.0.0", "567c03902920827a18a89f05b79a37b5bf93553154b883e0131801600cf02ce0", [:rebar3], [], "hexpm", "fc763185b932ecb32a554fb735ee03c3b6b1b31366077a2427d2a97f3bd26735"},
 }