diff --git a/src/Parameters/Concerns/GeneratesFromRules.php b/src/Parameters/Concerns/GeneratesFromRules.php
index ded1d55..51fcc95 100644
--- a/src/Parameters/Concerns/GeneratesFromRules.php
+++ b/src/Parameters/Concerns/GeneratesFromRules.php
@@ -62,11 +62,11 @@ protected function getEnumValues(array $paramRules)
     private function getInParameter(array $paramRules)
     {
         foreach ($paramRules as $rule) {
-            if (Str::startsWith($rule, 'in:')) {
+            if ((is_string($rule) || method_exists($rule , '__toString')) && Str::startsWith($rule, 'in:')) {
                 return $rule;
             }
         }
 
         return false;
     }
-}
\ No newline at end of file
+}
diff --git a/tests/Parameters/BodyParameterGeneratorTest.php b/tests/Parameters/BodyParameterGeneratorTest.php
index f8928fa..d168116 100644
--- a/tests/Parameters/BodyParameterGeneratorTest.php
+++ b/tests/Parameters/BodyParameterGeneratorTest.php
@@ -2,8 +2,10 @@
 
 namespace Mtrajano\LaravelSwagger\Tests\Parameters;
 
+use Illuminate\Validation\Rule;
 use Mtrajano\LaravelSwagger\Tests\TestCase;
 use Mtrajano\LaravelSwagger\Parameters\BodyParameterGenerator;
+use Mtrajano\LaravelSwagger\Tests\Stubs\Rules\Uppercase as UppercaseRule;
 
 class BodyParameterGeneratorTest extends TestCase
 {
@@ -153,6 +155,63 @@ public function testSingleObjectSyntax()
         ], $bodyParameters['schema']['properties']);
     }
 
+    public function testResolvesRuleEnum()
+    {
+
+        $bodyParameters = $this->getBodyParameters([
+            'type' => [
+                Rule::in(1,2,3),
+                'integer',
+            ]
+        ]);
+
+        $this->assertEquals([
+            'type' => [
+                'type' => 'integer',
+                'enum' => ['"1"','"2"','"3"'], //using Rule::in parameters are cast to string
+            ]
+        ], $bodyParameters['schema']['properties']);
+
+    }
+
+    public function testIgnoresRuleObject()
+    {
+
+        $bodyParameters = $this->getBodyParameters([
+            'name' => [
+                'string',
+                new UppercaseRule
+            ],
+        ]);
+
+        $this->assertEquals([
+            'name' => [
+                'type' => 'string',
+            ]
+        ], $bodyParameters['schema']['properties']);
+
+    }
+
+    public function testIgnoresClosureRules()
+    {
+        $bodyParameters = $this->getBodyParameters([
+            'name' => [
+                'string',
+                function ($attribute, $value, $fail) {
+                    if ($value === 'foo') {
+                        $fail($attribute.' is invalid.');
+                    }
+                },
+            ],
+        ]);
+
+        $this->assertEquals([
+            'name' => [
+                'type' => 'string',
+            ]
+        ], $bodyParameters['schema']['properties']);
+    }
+
     private function getBodyParameters(array $rules)
     {
         $bodyParameters = (new BodyParameterGenerator($rules))->getParameters();
diff --git a/tests/Stubs/Rules/Uppercase.php b/tests/Stubs/Rules/Uppercase.php
new file mode 100644
index 0000000..863e7de
--- /dev/null
+++ b/tests/Stubs/Rules/Uppercase.php
@@ -0,0 +1,30 @@
+<?php
+
+namespace Mtrajano\LaravelSwagger\Tests\Stubs\Rules;
+
+use Illuminate\Contracts\Validation\Rule;
+
+class Uppercase implements Rule
+{
+    /**
+     * Determine if the validation rule passes.
+     *
+     * @param  string  $attribute
+     * @param  mixed  $value
+     * @return bool
+     */
+    public function passes($attribute, $value)
+    {
+        return strtoupper($value) === $value;
+    }
+
+    /**
+     * Get the validation error message.
+     *
+     * @return string
+     */
+    public function message()
+    {
+        return 'The :attribute must be uppercase.';
+    }
+}
\ No newline at end of file