diff --git a/package.json b/package.json
index 14c5d0f5..147d9cd5 100644
--- a/package.json
+++ b/package.json
@@ -27,14 +27,15 @@
     "node": ">= 8.x"
   },
   "scripts": {
-    "test": "npm run prettier:check && npm run lint && npm run check && npm run testonly",
-    "test:ci": "yarn check --integrity && npm run prettier:check && npm run lint && npm run check && npm run testonly:cover && npm run build",
+    "test": "npm run prettier:check && npm run lint && npm run check && npm run check:ts && npm run testonly",
+    "test:ci": "yarn check --integrity && npm run prettier:check && npm run lint && npm run check && npm run check:ts && npm run testonly:cover && npm run build",
     "testonly": "mocha src/**/__tests__/**/*.js",
     "testonly:cover": "nyc npm run testonly",
     "lint": "eslint src resources",
     "prettier": "prettier --ignore-path .gitignore --write --list-different '**/*.{js,ts,md,json,yml}'",
-    "prettier:check": "prettier --ignore-path .gitignore --check '**/*.{js,md,json,yml}'",
+    "prettier:check": "prettier --ignore-path .gitignore --check '**/*.{js,ts,md,json,yml}'",
     "check": "flow check",
+    "check:ts": "dtslint types",
     "build": "node resources/build.js",
     "preversion": ". ./resources/checkgit.sh",
     "start": "node -r @babel/register examples/index.js"
@@ -50,6 +51,8 @@
     "@babel/plugin-transform-flow-strip-types": "7.4.4",
     "@babel/plugin-transform-modules-commonjs": "7.5.0",
     "@babel/register": "7.4.4",
+    "@types/graphql": "^14.2.2",
+    "@types/node": "^12.6.2",
     "babel-eslint": "10.0.2",
     "body-parser": "1.19.0",
     "chai": "4.2.0",
diff --git a/yarn.lock b/yarn.lock
index 8a7f30ef..ad06a4e3 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -217,6 +217,16 @@
   resolved "https://registry.yarnpkg.com/@sinonjs/text-encoding/-/text-encoding-0.7.1.tgz#8da5c6530915653f3a1f38fd5f101d8c3f8079c5"
   integrity sha512-+iTbntw2IZPb/anVDbypzfQa+ay64MW0Zo8aJ8gZPWMMK6/OubMVb6lUPMagqjOPnmtauXnFCACVl3O7ogjeqQ==
 
+"@types/graphql@^14.2.2":
+  version "14.2.2"
+  resolved "https://registry.yarnpkg.com/@types/graphql/-/graphql-14.2.2.tgz#10f197e6f8559c11b16d630c5e9c10c3c8e61c5e"
+  integrity sha512-okXbUmdZFMO3AYBEJCcpJFPFDkKmIiZZBqWD5TmPtAv+GHfjD2qLZEI0PvZ8IWMU4ozoK2HV2lDxWjw4LbVlnw==
+
+"@types/node@^12.6.2":
+  version "12.6.2"
+  resolved "https://registry.yarnpkg.com/@types/node/-/node-12.6.2.tgz#a5ccec6abb6060d5f20d256fb03ed743e9774999"
+  integrity sha512-gojym4tX0FWeV2gsW4Xmzo5wxGjXGm550oVUII7f7G5o4BV6c7DBdiG1RRQd+y1bvqRyYtPfMK85UM95vsapqQ==
+
 "@types/parsimmon@^1.3.0":
   version "1.10.0"
   resolved "https://registry.yarnpkg.com/@types/parsimmon/-/parsimmon-1.10.0.tgz#ffb81cb023ff435a41d4710a29ab23c561dc9fdf"