diff --git a/src/Processors/AugmentRequestBody.php b/src/Processors/AugmentRequestBody.php
index 104e6f1c8..dd9825a3d 100644
--- a/src/Processors/AugmentRequestBody.php
+++ b/src/Processors/AugmentRequestBody.php
@@ -58,6 +58,17 @@ protected function augmentRequestBody(Analysis $analysis, array $requestBodies):
                     $requestBody->ref = $schema->ref;
                 }
 
+                // Fall back: resolve parameter type to a Schema ref
+                if (Generator::isDefault($requestBody->ref)) {
+                    $type = $context->reflector->getType();
+                    if ($type instanceof \ReflectionNamedType && !$type->isBuiltin()) {
+                        $className = $type->getName();
+                        if ($schemaAnnotation = $analysis->getAnnotationForSource($className, OA\Schema::class)) {
+                            $requestBody->ref = OA\Components::ref($schemaAnnotation);
+                        }
+                    }
+                }
+
                 if (Generator::isDefault($requestBody->required)) {
                     $requestBody->required = !$schema->isNullable();
                 }
diff --git a/tests/Fixtures/Scratch/RequestBody.php b/tests/Fixtures/Scratch/RequestBody.php
index 2208bf20b..8feb5e018 100644
--- a/tests/Fixtures/Scratch/RequestBody.php
+++ b/tests/Fixtures/Scratch/RequestBody.php
@@ -89,4 +89,17 @@ public function postRef()
     public function postRefFoo(#[OAT\RequestBody] RequestBodyRefFoo $body)
     {
     }
+
+    #[OAT\Post(
+        path: '/endpoint/schema-param',
+        responses: [
+            new OAT\Response(
+                response: 200,
+                description: 'All good'
+            ),
+        ]
+    )]
+    public function postSchemaParam(#[OAT\RequestBody] RequestBodySchema $body)
+    {
+    }
 }
diff --git a/tests/Fixtures/Scratch/RequestBody3.0.0-legacy.yaml b/tests/Fixtures/Scratch/RequestBody3.0.0-legacy.yaml
index 9348b72ca..52e51b24b 100644
--- a/tests/Fixtures/Scratch/RequestBody3.0.0-legacy.yaml
+++ b/tests/Fixtures/Scratch/RequestBody3.0.0-legacy.yaml
@@ -43,6 +43,14 @@ paths:
       responses:
         '200':
           description: 'All good'
+  /endpoint/schema-param:
+    post:
+      operationId: e9325a4f940b91d3babe398eeebd8426
+      requestBody:
+        $ref: '#/components/schemas/RequestBodySchema'
+      responses:
+        '200':
+          description: 'All good'
 components:
   schemas:
     RequestBodySchema: {  }
diff --git a/tests/Fixtures/Scratch/RequestBody3.0.0-type-info.yaml b/tests/Fixtures/Scratch/RequestBody3.0.0-type-info.yaml
index 724732237..b26c96dd6 100644
--- a/tests/Fixtures/Scratch/RequestBody3.0.0-type-info.yaml
+++ b/tests/Fixtures/Scratch/RequestBody3.0.0-type-info.yaml
@@ -43,6 +43,14 @@ paths:
       responses:
         '200':
           description: 'All good'
+  /endpoint/schema-param:
+    post:
+      operationId: e9325a4f940b91d3babe398eeebd8426
+      requestBody:
+        $ref: '#/components/schemas/RequestBodySchema'
+      responses:
+        '200':
+          description: 'All good'
 components:
   schemas:
     RequestBodySchema: {  }
diff --git a/tests/Fixtures/Scratch/RequestBody3.1.0-legacy.yaml b/tests/Fixtures/Scratch/RequestBody3.1.0-legacy.yaml
index 8a0474e9c..a55ae7649 100644
--- a/tests/Fixtures/Scratch/RequestBody3.1.0-legacy.yaml
+++ b/tests/Fixtures/Scratch/RequestBody3.1.0-legacy.yaml
@@ -43,6 +43,14 @@ paths:
       responses:
         '200':
           description: 'All good'
+  /endpoint/schema-param:
+    post:
+      operationId: e9325a4f940b91d3babe398eeebd8426
+      requestBody:
+        $ref: '#/components/schemas/RequestBodySchema'
+      responses:
+        '200':
+          description: 'All good'
 components:
   schemas:
     RequestBodySchema: {  }
diff --git a/tests/Fixtures/Scratch/RequestBody3.1.0-type-info.yaml b/tests/Fixtures/Scratch/RequestBody3.1.0-type-info.yaml
index 7f2ae1812..e8e9039c1 100644
--- a/tests/Fixtures/Scratch/RequestBody3.1.0-type-info.yaml
+++ b/tests/Fixtures/Scratch/RequestBody3.1.0-type-info.yaml
@@ -43,6 +43,14 @@ paths:
       responses:
         '200':
           description: 'All good'
+  /endpoint/schema-param:
+    post:
+      operationId: e9325a4f940b91d3babe398eeebd8426
+      requestBody:
+        $ref: '#/components/schemas/RequestBodySchema'
+      responses:
+        '200':
+          description: 'All good'
 components:
   schemas:
     RequestBodySchema: {  }
diff --git a/tests/Fixtures/Scratch/RequestBody3.2.0-legacy.yaml b/tests/Fixtures/Scratch/RequestBody3.2.0-legacy.yaml
index d2b6b706f..d5e83e96b 100644
--- a/tests/Fixtures/Scratch/RequestBody3.2.0-legacy.yaml
+++ b/tests/Fixtures/Scratch/RequestBody3.2.0-legacy.yaml
@@ -43,6 +43,14 @@ paths:
       responses:
         '200':
           description: 'All good'
+  /endpoint/schema-param:
+    post:
+      operationId: e9325a4f940b91d3babe398eeebd8426
+      requestBody:
+        $ref: '#/components/schemas/RequestBodySchema'
+      responses:
+        '200':
+          description: 'All good'
 components:
   schemas:
     RequestBodySchema: {  }
diff --git a/tests/Fixtures/Scratch/RequestBody3.2.0-type-info.yaml b/tests/Fixtures/Scratch/RequestBody3.2.0-type-info.yaml
index d3e3a73a8..8e2539240 100644
--- a/tests/Fixtures/Scratch/RequestBody3.2.0-type-info.yaml
+++ b/tests/Fixtures/Scratch/RequestBody3.2.0-type-info.yaml
@@ -43,6 +43,14 @@ paths:
       responses:
         '200':
           description: 'All good'
+  /endpoint/schema-param:
+    post:
+      operationId: e9325a4f940b91d3babe398eeebd8426
+      requestBody:
+        $ref: '#/components/schemas/RequestBodySchema'
+      responses:
+        '200':
+          description: 'All good'
 components:
   schemas:
     RequestBodySchema: {  }