diff --git a/spec/routes/parameters.spec.ts b/spec/routes/parameters.spec.ts
index 9ea55f6..cdd7e88 100644
--- a/spec/routes/parameters.spec.ts
+++ b/spec/routes/parameters.spec.ts
@@ -21,14 +21,15 @@ describe('parameters', () => {
       ]);
     });
 
-    it('generates query parameter for route from object with refine', () => {
+    it('generates query parameter for route from object with effects', () => {
       const { parameters } = generateDataForRoute({
         request: {
           query: z
             .object({
               filter: z.string(),
             })
-            .refine(({ filter }) => filter.length > 3),
+            .refine(({ filter }) => filter.length > 3)
+            .transform(d => d),
         },
       });
 
@@ -142,14 +143,15 @@ describe('parameters', () => {
       ]);
     });
 
-    it('generates path parameter for route from object with refine', () => {
+    it('generates path parameter for route from object with effects', () => {
       const { parameters } = generateDataForRoute({
         request: {
           params: z
             .object({
               filter: z.string(),
             })
-            .refine(({ filter }) => filter.length > 3),
+            .refine(({ filter }) => filter.length > 3)
+            .transform(d => d),
         },
       });
 
@@ -244,14 +246,15 @@ describe('parameters', () => {
       ]);
     });
 
-    it('generates cookie parameter for route from object with refine', () => {
+    it('generates cookie parameter for route from object with effects', () => {
       const { parameters } = generateDataForRoute({
         request: {
           cookies: z
             .object({
               filter: z.string(),
             })
-            .refine(({ filter }) => filter.length > 3),
+            .refine(({ filter }) => filter.length > 3)
+            .transform(d => d),
         },
       });
 
@@ -367,14 +370,15 @@ describe('parameters', () => {
       ]);
     });
 
-    it('generates header parameter for route from object with refine', () => {
+    it('generates header parameter for route from object with effects', () => {
       const { parameters } = generateDataForRoute({
         request: {
           headers: z
             .object({
               filter: z.string(),
             })
-            .refine(({ filter }) => filter.length > 3),
+            .refine(({ filter }) => filter.length > 3)
+            .transform(d => d),
         },
       });
 
diff --git a/src/openapi-generator.ts b/src/openapi-generator.ts
index c4b2b27..66d29d9 100644
--- a/src/openapi-generator.ts
+++ b/src/openapi-generator.ts
@@ -545,12 +545,14 @@ export class OpenAPIGenerator {
     ];
   }
 
-  private cleanParameter(schema: RouteParameter) {
+  private cleanParameter(schema: RouteParameter): AnyZodObject | undefined {
     if (!schema) {
       return undefined;
     }
 
-    return isZodType(schema, 'ZodEffects') ? schema._def.schema : schema;
+    return isZodType(schema, 'ZodEffects')
+      ? this.cleanParameter(schema._def.schema)
+      : schema;
   }
 
   generatePath(route: RouteConfig): PathItemObject {
diff --git a/src/openapi-registry.ts b/src/openapi-registry.ts
index 4e6e6e8..f92dcb4 100644
--- a/src/openapi-registry.ts
+++ b/src/openapi-registry.ts
@@ -102,10 +102,11 @@ export interface ResponseConfig {
   content?: ZodContentObject;
 }
 
-export type RouteParameter =
+type ZodObjectWithEffect =
   | AnyZodObject
-  | ZodEffects<AnyZodObject, unknown, unknown>
-  | undefined;
+  | ZodEffects<ZodObjectWithEffect, unknown, unknown>;
+
+export type RouteParameter = ZodObjectWithEffect | undefined;
 
 export type RouteConfig = Omit<OperationObject, 'responses'> & {
   method: Method;