diff --git a/package.json b/package.json
index 32a4d08..d6f58e2 100644
--- a/package.json
+++ b/package.json
@@ -16,7 +16,7 @@
   ],
   "devDependencies": {
     "coveralls": "3.0.4",
-    "koa": "2.7.0",
+    "koa": "2.13.1",
     "koa-mount": "4.0.0",
     "mocha": "6.1.4",
     "mocha-lcov-reporter": "1.3.0",
diff --git a/yarn.lock b/yarn.lock
index f082075..92f7289 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -339,13 +339,13 @@ cookiejar@^2.1.0:
   resolved "https://registry.yarnpkg.com/cookiejar/-/cookiejar-2.1.2.tgz#dd8a235530752f988f9a0844f3fc589e3111125c"
   integrity sha512-Mw+adcfzPxcPeI+0WlvRrr/3lGVO0bD75SxX6811cxSh1Wbxx7xZBGK1eVtDf6si8rg2lhnUjsVLMFMfbRIuwA==
 
-cookies@~0.7.1:
-  version "0.7.3"
-  resolved "https://registry.yarnpkg.com/cookies/-/cookies-0.7.3.tgz#7912ce21fbf2e8c2da70cf1c3f351aecf59dadfa"
-  integrity sha512-+gixgxYSgQLTaTIilDHAdlNPZDENDQernEMiIcZpYYP14zgHsCt4Ce1FEjFtcp6GefhozebB6orvhAAWx/IS0A==
+cookies@~0.8.0:
+  version "0.8.0"
+  resolved "https://registry.yarnpkg.com/cookies/-/cookies-0.8.0.tgz#1293ce4b391740a8406e3c9870e828c4b54f3f90"
+  integrity sha512-8aPsApQfebXnuI+537McwYsDtjVxGm8gTIzQI3FDW6t5t/DAhERxtnbEPN/8RX+uZthoz4eCOgloXaE5cYyNow==
   dependencies:
-    depd "~1.1.2"
-    keygrip "~1.0.3"
+    depd "~2.0.0"
+    keygrip "~1.1.0"
 
 core-util-is@1.0.2, core-util-is@~1.0.0:
   version "1.0.2"
@@ -456,7 +456,12 @@ delegates@^1.0.0:
   resolved "https://registry.yarnpkg.com/delegates/-/delegates-1.0.0.tgz#84c6e159b81904fdca59a0ef44cd870d31250f9a"
   integrity sha1-hMbhWbgZBP3KWaDvRM2HDTElD5o=
 
-depd@^1.1.2, depd@~1.1.2:
+depd@^2.0.0, depd@~2.0.0:
+  version "2.0.0"
+  resolved "https://registry.yarnpkg.com/depd/-/depd-2.0.0.tgz#b696163cc757560d09cf22cc8fad1571b79e76df"
+  integrity sha512-g7nH6P6dyDioJogAAGprGpCtVImJhpPk/roCzdb3fIh61/s/nPsfR6onyMwkCAR/OlC3yBC0lESvUoQEAssIrw==
+
+depd@~1.1.2:
   version "1.1.2"
   resolved "https://registry.yarnpkg.com/depd/-/depd-1.1.2.tgz#9bcd52e14c097763e749b274c4346ed2e560b5a9"
   integrity sha1-m81S4UwJd2PnSbJ0xDRu0uVgtak=
@@ -489,6 +494,11 @@ emoji-regex@^7.0.1:
   resolved "https://registry.yarnpkg.com/emoji-regex/-/emoji-regex-7.0.3.tgz#933a04052860c85e83c122479c4748a8e4c72156"
   integrity sha512-CwBLREIQ7LvYFB0WyRvwhq5N5qPhc6PMjD6bYggFlI5YyDgl+0vxq5VHbMOFqLg7hfWzmu8T5Z1QofhmTIhItA==
 
+encodeurl@^1.0.2:
+  version "1.0.2"
+  resolved "https://registry.yarnpkg.com/encodeurl/-/encodeurl-1.0.2.tgz#ad3ff4c86ec2d029322f5a02c3a9a606c95b3f59"
+  integrity sha1-rT/0yG7C0CkyL1oCw6mmBslbP1k=
+
 end-of-stream@^1.1.0:
   version "1.4.1"
   resolved "https://registry.yarnpkg.com/end-of-stream/-/end-of-stream-1.4.1.tgz#ed29634d19baba463b6ce6b80a37213eab71ec43"
@@ -503,11 +513,6 @@ error-ex@^1.3.1:
   dependencies:
     is-arrayish "^0.2.1"
 
-error-inject@^1.0.0:
-  version "1.0.0"
-  resolved "https://registry.yarnpkg.com/error-inject/-/error-inject-1.0.0.tgz#e2b3d91b54aed672f309d950d154850fa11d4f37"
-  integrity sha1-4rPZG1Su1nLzCdlQ0VSFD6EdTzc=
-
 es-abstract@^1.5.1:
   version "1.13.0"
   resolved "https://registry.yarnpkg.com/es-abstract/-/es-abstract-1.13.0.tgz#ac86145fdd5099d8dd49558ccba2eaf9b88e24e9"
@@ -1020,10 +1025,12 @@ jsprim@^1.2.2:
     json-schema "0.2.3"
     verror "1.10.0"
 
-keygrip@~1.0.3:
-  version "1.0.3"
-  resolved "https://registry.yarnpkg.com/keygrip/-/keygrip-1.0.3.tgz#399d709f0aed2bab0a059e0cdd3a5023a053e1dc"
-  integrity sha512-/PpesirAIfaklxUzp4Yb7xBper9MwP6hNRA6BGGUFCgbJ+BM5CKBtsoxinNXkLHAr+GXS1/lSlF2rP7cv5Fl+g==
+keygrip@~1.1.0:
+  version "1.1.0"
+  resolved "https://registry.yarnpkg.com/keygrip/-/keygrip-1.1.0.tgz#871b1681d5e159c62a445b0c74b615e0917e7226"
+  integrity sha512-iYSchDJ+liQ8iwbSI2QqsQOvqv58eJCEanyJPJi+Khyu8smkcKSFUCbPwzFcL7YVtZ6eONjqRX/38caJ7QjRAQ==
+  dependencies:
+    tsscmp "1.0.6"
 
 koa-compose@^3.0.0:
   version "3.2.1"
@@ -1045,11 +1052,6 @@ koa-convert@^1.2.0:
     co "^4.6.0"
     koa-compose "^3.0.0"
 
-koa-is-json@^1.0.0:
-  version "1.0.0"
-  resolved "https://registry.yarnpkg.com/koa-is-json/-/koa-is-json-1.0.0.tgz#273c07edcdcb8df6a2c1ab7d59ee76491451ec14"
-  integrity sha1-JzwH7c3Ljfaiwat9We52SRRR7BQ=
-
 koa-mount@4.0.0:
   version "4.0.0"
   resolved "https://registry.yarnpkg.com/koa-mount/-/koa-mount-4.0.0.tgz#e0265e58198e1a14ef889514c607254ff386329c"
@@ -1058,21 +1060,21 @@ koa-mount@4.0.0:
     debug "^4.0.1"
     koa-compose "^4.1.0"
 
-koa@2.7.0:
-  version "2.7.0"
-  resolved "https://registry.yarnpkg.com/koa/-/koa-2.7.0.tgz#7e00843506942b9d82c6cc33749f657c6e5e7adf"
-  integrity sha512-7ojD05s2Q+hFudF8tDLZ1CpCdVZw8JQELWSkcfG9bdtoTDzMmkRF6BQBU7JzIzCCOY3xd3tftiy/loHBUYaY2Q==
+koa@2.13.1:
+  version "2.13.1"
+  resolved "https://registry.yarnpkg.com/koa/-/koa-2.13.1.tgz#6275172875b27bcfe1d454356a5b6b9f5a9b1051"
+  integrity sha512-Lb2Dloc72auj5vK4X4qqL7B5jyDPQaZucc9sR/71byg7ryoD1NCaCm63CShk9ID9quQvDEi1bGR/iGjCG7As3w==
   dependencies:
     accepts "^1.3.5"
     cache-content-type "^1.0.0"
     content-disposition "~0.5.2"
     content-type "^1.0.4"
-    cookies "~0.7.1"
+    cookies "~0.8.0"
     debug "~3.1.0"
     delegates "^1.0.0"
-    depd "^1.1.2"
+    depd "^2.0.0"
     destroy "^1.0.4"
-    error-inject "^1.0.0"
+    encodeurl "^1.0.2"
     escape-html "^1.0.3"
     fresh "~0.5.2"
     http-assert "^1.3.0"
@@ -1080,7 +1082,6 @@ koa@2.7.0:
     is-generator-function "^1.0.7"
     koa-compose "^4.1.0"
     koa-convert "^1.2.0"
-    koa-is-json "^1.0.0"
     on-finished "^2.3.0"
     only "~0.0.2"
     parseurl "^1.3.2"
@@ -1960,6 +1961,11 @@ trim-right@^1.0.1:
   resolved "https://registry.yarnpkg.com/trim-right/-/trim-right-1.0.1.tgz#cb2e1203067e0c8de1f614094b9fe45704ea6003"
   integrity sha1-yy4SAwZ+DI3h9hQJS5/kVwTqYAM=
 
+tsscmp@1.0.6:
+  version "1.0.6"
+  resolved "https://registry.yarnpkg.com/tsscmp/-/tsscmp-1.0.6.tgz#85b99583ac3589ec4bfef825b5000aa911d605eb"
+  integrity sha512-LxhtAkPDTkVCMQjt2h6eBVY28KCjikZqZfMcC15YBeNjkgUpdCfBu5HoiOTDu86v6smE8yOjyEktJ8hlbANHQA==
+
 tunnel-agent@^0.6.0:
   version "0.6.0"
   resolved "https://registry.yarnpkg.com/tunnel-agent/-/tunnel-agent-0.6.0.tgz#27a5dea06b36b04a0a9966774b290868f0fc40fd"