diff --git a/striker-ui-api/src/lib/join.ts b/striker-ui-api/src/lib/join.ts
index 51e91783..bdf05e75 100644
--- a/striker-ui-api/src/lib/join.ts
+++ b/striker-ui-api/src/lib/join.ts
@@ -1,13 +1,13 @@
 import call from './call';
 
-const join = (
-  elements: string[] | string | undefined,
+const join: JoinFunction = (
+  elements,
   {
     beforeReturn,
     elementWrapper = '',
     onEach = (element: string) => element,
     separator = '',
-  }: JoinOptions = {},
+  } = {},
 ) => {
   const joinSeparator = `${elementWrapper}${separator}${elementWrapper}`;
 
diff --git a/striker-ui-api/src/types/JoinOptions.d.ts b/striker-ui-api/src/types/JoinFunction.d.ts
similarity index 58%
rename from striker-ui-api/src/types/JoinOptions.d.ts
rename to striker-ui-api/src/types/JoinFunction.d.ts
index 6a968f5a..9039e103 100644
--- a/striker-ui-api/src/types/JoinOptions.d.ts
+++ b/striker-ui-api/src/types/JoinFunction.d.ts
@@ -4,3 +4,8 @@ type JoinOptions = {
   onEach?: (element: string) => string;
   separator?: string;
 };
+
+type JoinFunction = (
+  elements: string[] | string | undefined,
+  options?: JoinOptions,
+) => string | undefined;