diff --git a/composer.json b/composer.json
index 3f573380..81e0ebe3 100644
--- a/composer.json
+++ b/composer.json
@@ -23,7 +23,7 @@
     "require": {
         "php": ">=7.2",
         "ext-json": "*",
-        "cebe/php-openapi": "^1.3",
+        "cebe/php-openapi": "^1.6",
         "league/uri": "^6.3",
         "psr/cache": "^1.0 || ^2.0 || ^3.0",
         "psr/http-message": "^1.0",
diff --git a/src/Schema/SchemaValidator.php b/src/Schema/SchemaValidator.php
index 55471b44..f1f75937 100644
--- a/src/Schema/SchemaValidator.php
+++ b/src/Schema/SchemaValidator.php
@@ -57,7 +57,7 @@ public function validate($data, CebeSchema $schema, ?BreadCrumb $breadCrumb = nu
 
         try {
             // These keywords are not part of the JSON Schema at all (new to OAS)
-            (new Nullable($schema))->validate($data, $schema->nullable);
+            (new Nullable($schema))->validate($data, $schema->nullable ?? true);
 
             // We don't want to validate any more if the value is a valid Null
             if ($data === null) {
diff --git a/tests/FromCommunity/IssueWithNullableMergeTest.php b/tests/FromCommunity/IssueWithNullableMergeTest.php
new file mode 100644
index 00000000..9a73f0d5
--- /dev/null
+++ b/tests/FromCommunity/IssueWithNullableMergeTest.php
@@ -0,0 +1,72 @@
+<?php
+
+declare(strict_types=1);
+
+namespace League\OpenAPIValidation\Tests\FromCommunity;
+
+use GuzzleHttp\Psr7\Response;
+use League\OpenAPIValidation\PSR7\OperationAddress;
+use League\OpenAPIValidation\PSR7\ValidatorBuilder;
+use League\OpenAPIValidation\Tests\PSR7\BaseValidatorTest;
+
+final class IssueWithNullableMergeTest extends BaseValidatorTest
+{
+    public function testNullableMergeOneOf(): void
+    {
+        $yaml = /** @lang yaml */
+            <<<'YAML'
+openapi: 3.0.0
+paths:
+  /api/nullable-merge:
+    get:
+      description: 'Test'
+      responses:
+        '200':
+          description: 'ok'
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/Thing"
+components:
+  schemas:
+    FooResult:
+      type: object
+      properties:
+        id:
+          type: integer
+        foo:
+          type: string
+    BarResult:
+      type: object
+      nullable: true
+      properties:
+        id:
+          type: integer
+        bar:
+          type: string
+    Thing:
+      type: object
+      properties:
+        result:
+          oneOf:
+            - $ref: "#/components/schemas/FooResult"
+            - $ref: "#/components/schemas/BarResult"
+YAML;
+
+        $validator = (new ValidatorBuilder())->fromYaml($yaml)->getResponseValidator();
+        $operation = new OperationAddress('/api/nullable-merge', 'get');
+
+        $responseContent = /** @lang JSON */
+            '
+    {
+      "result": null
+    }
+';
+
+        $response = new Response(200, ['Content-Type' => 'application/json'], $responseContent);
+
+        $validator->validate($operation, $response);
+
+        $this->addToAssertionCount(1);
+    }
+}
diff --git a/tests/FromCommunity/NullableSchemaTest.php b/tests/FromCommunity/NullableSchemaTest.php
new file mode 100644
index 00000000..223b0004
--- /dev/null
+++ b/tests/FromCommunity/NullableSchemaTest.php
@@ -0,0 +1,62 @@
+<?php
+
+declare(strict_types=1);
+
+namespace League\OpenAPIValidation\Tests\FromCommunity;
+
+use GuzzleHttp\Psr7\Response;
+use League\OpenAPIValidation\PSR7\OperationAddress;
+use League\OpenAPIValidation\PSR7\ValidatorBuilder;
+use League\OpenAPIValidation\Tests\PSR7\BaseValidatorTest;
+
+final class NullableSchemaTest extends BaseValidatorTest
+{
+    public function testNullableImplicitResult(): void
+    {
+        $yaml = /** @lang yaml */
+            <<<'YAML'
+openapi: 3.0.0
+paths:
+  /api/nullable:
+    get:
+      description: 'Test'
+      responses:
+        '200':
+          description: 'ok'
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/Thing"
+components:
+  schemas:
+    FooResult:
+      properties:
+        id:
+          type: integer
+        foo:
+          type: string
+    Thing:
+      type: object
+      properties:
+        result:
+          schema:
+            - $ref: "#/components/schemas/FooResult"
+YAML;
+
+        $validator = (new ValidatorBuilder())->fromYaml($yaml)->getResponseValidator();
+        $operation = new OperationAddress('/api/nullable', 'get');
+
+        $responseContent = /** @lang JSON */
+            '
+{
+  "result": null
+}
+';
+
+        $response = new Response(200, ['Content-Type' => 'application/json'], $responseContent);
+
+        $validator->validate($operation, $response);
+
+        $this->addToAssertionCount(1);
+    }
+}