diff --git a/src/converter/plugins/convertFunctionType.ts b/src/converter/plugins/convertFunctionType.ts
index 32eb1989..5d36c5dc 100644
--- a/src/converter/plugins/convertFunctionType.ts
+++ b/src/converter/plugins/convertFunctionType.ts
@@ -15,15 +15,15 @@ export const convertFunctionType = createSimplePlugin((node, context, render) =>
         return `Function<Any?> /* ${typeScriptService?.printNode(node)} */`
     }
 
+    const returnType = render(node.type)
+
     if (node.parameters.some(parameter => parameter.dotDotDotToken)) {
-        return `Function<Any?> /* ${typeScriptService?.printNode(node)} */`
+        return `Function<${returnType}> /* ${typeScriptService?.printNode(node)} */`
     }
 
     const parameters = node.parameters
         ?.map(parameter => render(parameter))
         ?.join(", ")
 
-    const returnType = render(node.type)
-
     return `(${parameters}) -> ${returnType}`
 })
diff --git a/test/functional/base/generated/function/vararg.kt b/test/functional/base/generated/function/vararg.kt
index e9d20099..93ca7fb4 100644
--- a/test/functional/base/generated/function/vararg.kt
+++ b/test/functional/base/generated/function/vararg.kt
@@ -13,4 +13,4 @@ external fun simpleVararg(vararg args: String): Unit
 
 external fun <T : Array<String>> genericVararg(vararg args: Any? /* T */): Unit
 
-external fun callbackVararg(fn: Function<Any?> /* (...args: string[]) => void */): Unit
+external fun callbackVararg(fn: Function<Unit> /* (...args: string[]) => void */): Unit