diff --git a/lib/vivid/png/buffer.ex b/lib/vivid/png/buffer.ex
index 087e0cd..1cfcbcb 100644
--- a/lib/vivid/png/buffer.ex
+++ b/lib/vivid/png/buffer.ex
@@ -13,8 +13,7 @@ defimpl Vivid.PNG, for: Vivid.Buffer do
     with {:ok, file} <- File.open(path, [:write]),
          png <- create_png(buffer, file),
          :ok <- :png.close(png),
-         :ok <- File.close(file),
-         do: :ok
+         do: File.close(file)
   end
 
   defp config(%Buffer{rows: height, columns: width}, file) do
diff --git a/mix.lock b/mix.lock
index a72fc21..a7fe570 100644
--- a/mix.lock
+++ b/mix.lock
@@ -1,6 +1,6 @@
 %{
   "bunt": {:hex, :bunt, "0.2.0", "951c6e801e8b1d2cbe58ebbd3e616a869061ddadcc4863d0a2182541acae9a38", [:mix], [], "hexpm", "7af5c7e09fe1d40f76c8e4f9dd2be7cebd83909f31fee7cd0e9eadc567da8353"},
-  "credo": {:hex, :credo, "1.5.4", "9914180105b438e378e94a844ec3a5088ae5875626fc945b7c1462b41afc3198", [:mix], [{:bunt, "~> 0.2.0", [hex: :bunt, repo: "hexpm", optional: false]}, {:file_system, "~> 0.2.8", [hex: :file_system, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: false]}], "hexpm", "cf51af45eadc0a3f39ba13b56fdac415c91b34f7b7533a13dc13550277141bc4"},
+  "credo": {:hex, :credo, "1.6.1", "7dc76dcdb764a4316c1596804c48eada9fff44bd4b733a91ccbf0c0f368be61e", [:mix], [{:bunt, "~> 0.2.0", [hex: :bunt, repo: "hexpm", optional: false]}, {:file_system, "~> 0.2.8", [hex: :file_system, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: false]}], "hexpm", "698607fb5993720c7e93d2d8e76f2175bba024de964e160e2f7151ef3ab82ac5"},
   "earmark": {:hex, :earmark, "1.3.2", "b840562ea3d67795ffbb5bd88940b1bed0ed9fa32834915125ea7d02e35888a5", [:mix], [], "hexpm", "e3be2bc3ae67781db529b80aa7e7c49904a988596e2dbff897425b48b3581161"},
   "earmark_parser": {:hex, :earmark_parser, "1.4.12", "b245e875ec0a311a342320da0551da407d9d2b65d98f7a9597ae078615af3449", [:mix], [], "hexpm", "711e2cc4d64abb7d566d43f54b78f7dc129308a63bc103fbd88550d2174b3160"},
   "ex_doc": {:hex, :ex_doc, "0.23.0", "a069bc9b0bf8efe323ecde8c0d62afc13d308b1fa3d228b65bca5cf8703a529d", [:mix], [{:earmark_parser, "~> 1.4.0", [hex: :earmark_parser, repo: "hexpm", optional: false]}, {:makeup_elixir, "~> 0.14", [hex: :makeup_elixir, repo: "hexpm", optional: false]}], "hexpm", "f5e2c4702468b2fd11b10d39416ddadd2fcdd173ba2a0285ebd92c39827a5a16"},