diff --git a/types/url-assembler/index.d.ts b/types/url-assembler/index.d.ts
index 3f33bf921a..e27fbbe58d 100644
--- a/types/url-assembler/index.d.ts
+++ b/types/url-assembler/index.d.ts
@@ -7,8 +7,8 @@ interface UrlAssembler {
 	template(template: string): UrlAssembler;
 	prefix(subPath: string): UrlAssembler;
 	segment(subPathTemplate: string): UrlAssembler;
-	param(key: string, value: string, strict: boolean): UrlAssembler;
-	param(params: {[s: string]: any}, strict: boolean): UrlAssembler;
+	param(key: string, value: string, strict?: boolean): UrlAssembler;
+	param(params: {[s: string]: any}, strict?: boolean): UrlAssembler;
 	query(key: string, value: any): UrlAssembler;
 	query(params: {[s: string]: any}): UrlAssembler;
 	toString(): string;