diff --git a/package.json b/package.json
index 3ea869e5e..967be291b 100644
--- a/package.json
+++ b/package.json
@@ -41,20 +41,20 @@
     "commander": "~2.20.0",
     "glob": "~7.1.4",
     "json-stable-stringify": "^1.0.1",
-    "typescript": "~3.4.5"
+    "typescript": "~3.5.1"
   },
   "devDependencies": {
     "@types/glob": "^7.1.1",
     "@types/jest": "^24.0.13",
     "@types/json-stable-stringify": "^1.0.32",
-    "@types/node": "^12.0.2",
+    "@types/node": "^12.0.3",
     "ajv": "~6.10.0",
     "chai": "~4.2.0",
     "jest": "^24.8.0",
     "jest-junit": "^6.4.0",
     "source-map-support": "~0.5.12",
     "ts-jest": "^24.0.2",
-    "ts-node": "^8.1.1",
+    "ts-node": "^8.2.0",
     "tslint": "~5.16.0"
   },
   "scripts": {
diff --git a/src/TypeFormatter/AnnotatedTypeFormatter.ts b/src/TypeFormatter/AnnotatedTypeFormatter.ts
index f11fffbb9..aeb0a1a48 100644
--- a/src/TypeFormatter/AnnotatedTypeFormatter.ts
+++ b/src/TypeFormatter/AnnotatedTypeFormatter.ts
@@ -35,10 +35,9 @@ export function makeNullable(def: Definition) {
             }
         }
 
-        for (const k in def) {
-            if (def.hasOwnProperty(k) && k !== "description" && k !== "title" && k !== "default") {
-                const key: keyof Definition = k as keyof Definition;
-                subdef[key] = def[key];
+        for (const key of Object.keys(def) as (keyof Definition)[]) {
+            if (key !== "description" && key !== "title" && key !== "default") {
+                subdef[key] = def[key] as any;
                 delete def[key];
             }
         }
diff --git a/yarn.lock b/yarn.lock
index 5c93d56fe..343d7babb 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -374,10 +374,10 @@
   resolved "https://registry.yarnpkg.com/@types/minimatch/-/minimatch-3.0.3.tgz#3dca0e3f33b200fc7d1139c0cd96c1268cadfd9d"
   integrity sha512-tHq6qdbT9U1IRSGf14CL0pUlULksvY9OZ+5eEgl1N7t+OA3tGvNpxJCzuKQlsNgCVwbAs670L1vcVQi8j9HjnA==
 
-"@types/node@*", "@types/node@^12.0.2":
-  version "12.0.2"
-  resolved "https://registry.yarnpkg.com/@types/node/-/node-12.0.2.tgz#3452a24edf9fea138b48fad4a0a028a683da1e40"
-  integrity sha512-5tabW/i+9mhrfEOUcLDu2xBPsHJ+X5Orqy9FKpale3SjDA17j5AEpYq5vfy3oAeAHGcvANRCO3NV3d2D6q3NiA==
+"@types/node@*", "@types/node@^12.0.3":
+  version "12.0.3"
+  resolved "https://registry.yarnpkg.com/@types/node/-/node-12.0.3.tgz#5d8d24e0033fc6393efadc85cb59c1f638095c9a"
+  integrity sha512-zkOxCS/fA+3SsdA+9Yun0iANxzhQRiNwTvJSr6N95JhuJ/x27z9G2URx1Jpt3zYFfCGUXZGL5UDxt5eyLE7wgw==
 
 "@types/stack-utils@^1.0.1":
   version "1.0.1"
@@ -2849,9 +2849,9 @@ prompts@^2.0.1:
     sisteransi "^1.0.0"
 
 psl@^1.1.24, psl@^1.1.28:
-  version "1.1.31"
-  resolved "https://registry.yarnpkg.com/psl/-/psl-1.1.31.tgz#e9aa86d0101b5b105cbe93ac6b784cd547276184"
-  integrity sha512-/6pt4+C+T+wZUieKR620OpzN/LlnNKuWjy1iFLQ/UG35JqHlR/89MP1d96dUfkf6Dne3TuLQzOYEYshJ+Hx8mw==
+  version "1.1.32"
+  resolved "https://registry.yarnpkg.com/psl/-/psl-1.1.32.tgz#3f132717cf2f9c169724b2b6caf373cf694198db"
+  integrity sha512-MHACAkHpihU/REGGPLj4sEfc/XKW2bheigvHO1dUqjaKigMp1C8+WLQYRGgeKFMsw5PMfegZcaN8IDXK/cD0+g==
 
 pump@^3.0.0:
   version "3.0.0"
@@ -3097,9 +3097,9 @@ sax@^1.2.4:
   integrity sha512-Ya52jSX2u7QKghxeoFGpLwCtGlt7j0oY9DYb5apt9nPlJ42ID+ulTXESnt/qAQcoSERyZ5sl3LDIOw0nAn/5DA==
 
 semver@^6.0.0:
-  version "6.1.0"
-  resolved "https://registry.yarnpkg.com/semver/-/semver-6.1.0.tgz#e95dc415d45ecf03f2f9f83b264a6b11f49c0cca"
-  integrity sha512-kCqEOOHoBcFs/2Ccuk4Xarm/KiWRSLEX9CAZF8xkJ6ZPlIoTZ8V5f7J16vYLJqDbR7KrxTJpR2lqjIEm2Qx9cQ==
+  version "6.1.1"
+  resolved "https://registry.yarnpkg.com/semver/-/semver-6.1.1.tgz#53f53da9b30b2103cd4f15eab3a18ecbcb210c9b"
+  integrity sha512-rWYq2e5iYW+fFe/oPPtYJxYgjBm8sC4rmoGdUOgBB7VnwKt6HrL793l2voH1UlsyYZpJ4g0wfjnTEO1s1NP2eQ==
 
 set-blocking@^2.0.0, set-blocking@~2.0.0:
   version "2.0.0"
@@ -3486,10 +3486,10 @@ ts-jest@^24.0.2:
     semver "^5.5"
     yargs-parser "10.x"
 
-ts-node@^8.1.1:
-  version "8.1.1"
-  resolved "https://registry.yarnpkg.com/ts-node/-/ts-node-8.1.1.tgz#2b9621934a0471f0e13c1b75be54ee0f46c31479"
-  integrity sha512-nd+mdxDP2BjQlyumBCMSU3IQLEjSla1X3uSzDfQ4M5OEZ3iDC01gjhs0FX29jyolATwLKB7YoRJ1Asbxd9EEoA==
+ts-node@^8.2.0:
+  version "8.2.0"
+  resolved "https://registry.yarnpkg.com/ts-node/-/ts-node-8.2.0.tgz#4a89754b00560bb24cd54526e1685fa38c45f240"
+  integrity sha512-m8XQwUurkbYqXrKqr3WHCW310utRNvV5OnRVeISeea7LoCWVcdfeB/Ntl8JYWFh+WRoUAdBgESrzKochQt7sMw==
   dependencies:
     arg "^4.1.0"
     diff "^4.0.1"
@@ -3552,10 +3552,10 @@ type-detect@^4.0.0, type-detect@^4.0.5:
   resolved "https://registry.yarnpkg.com/type-detect/-/type-detect-4.0.8.tgz#7646fb5f18871cfbb7749e69bd39a6388eb7450c"
   integrity sha512-0fr/mIH1dlO+x7TlcMy+bIDqKPsw/70tVyeHW787goQjhmqaZe10uwLujubK9q9Lg6Fiho1KUKDYz0Z7k7g5/g==
 
-typescript@~3.4.5:
-  version "3.4.5"
-  resolved "https://registry.yarnpkg.com/typescript/-/typescript-3.4.5.tgz#2d2618d10bb566572b8d7aad5180d84257d70a99"
-  integrity sha512-YycBxUb49UUhdNMU5aJ7z5Ej2XGmaIBL0x34vZ82fn3hGvD+bgrMrVDpatgz2f7YxUMJxMkbWxJZeAvDxVe7Vw==
+typescript@~3.5.1:
+  version "3.5.1"
+  resolved "https://registry.yarnpkg.com/typescript/-/typescript-3.5.1.tgz#ba72a6a600b2158139c5dd8850f700e231464202"
+  integrity sha512-64HkdiRv1yYZsSe4xC1WVgamNigVYjlssIoaH2HcZF0+ijsk5YK2g0G34w9wJkze8+5ow4STd22AynfO6ZYYLw==
 
 uglify-js@^3.1.4:
   version "3.5.15"