diff --git a/packages/oats/package.json b/packages/oats/package.json
index f3a441e8..262be0b7 100644
--- a/packages/oats/package.json
+++ b/packages/oats/package.json
@@ -27,7 +27,7 @@
   "dependencies": {
     "js-yaml": "^4.0.0",
     "lodash": "^4.17.20",
-    "openapi3-ts": "^3.0.0"
+    "openapi3-ts": "^4.0.0"
   },
   "keywords": [
     "oats",
diff --git a/packages/oats/src/driver.ts b/packages/oats/src/driver.ts
index de4cc0c5..46e7005a 100644
--- a/packages/oats/src/driver.ts
+++ b/packages/oats/src/driver.ts
@@ -4,7 +4,7 @@ import * as types from './generate-types';
 import { AdditionalPropertiesIndexSignature, Resolve } from './generate-types';
 import * as server from './generate-server';
 import * as path from 'path';
-import * as oas from 'openapi3-ts';
+import { oas31 as oas } from 'openapi3-ts';
 import {
   capitalize,
   NameKind,
diff --git a/packages/oats/src/generate-server.ts b/packages/oats/src/generate-server.ts
index 9a3e482d..422c018c 100644
--- a/packages/oats/src/generate-server.ts
+++ b/packages/oats/src/generate-server.ts
@@ -1,4 +1,4 @@
-import * as oas from 'openapi3-ts';
+import { oas31 as oas } from 'openapi3-ts';
 import * as ts from 'typescript';
 import * as assert from 'assert';
 import * as oautil from './util';
diff --git a/packages/oats/src/generate-types.ts b/packages/oats/src/generate-types.ts
index 6707482d..043cdeec 100644
--- a/packages/oats/src/generate-types.ts
+++ b/packages/oats/src/generate-types.ts
@@ -1,4 +1,4 @@
-import * as oas from 'openapi3-ts';
+import { oas31 as oas } from 'openapi3-ts';
 import * as ts from 'typescript';
 import * as _ from 'lodash';
 import * as assert from 'assert';
diff --git a/packages/oats/src/util.ts b/packages/oats/src/util.ts
index 68064bb2..95d6d6f4 100644
--- a/packages/oats/src/util.ts
+++ b/packages/oats/src/util.ts
@@ -1,4 +1,4 @@
-import * as oas from 'openapi3-ts';
+import { oas31 as oas } from 'openapi3-ts';
 import * as assert from 'assert';
 import * as _ from 'lodash';