diff --git a/FirebaseVertexAI/Sources/FunctionCalling.swift b/FirebaseVertexAI/Sources/FunctionCalling.swift
index f9f74ee2e99..d3b5e2da61e 100644
--- a/FirebaseVertexAI/Sources/FunctionCalling.swift
+++ b/FirebaseVertexAI/Sources/FunctionCalling.swift
@@ -131,7 +131,7 @@ public struct FunctionDeclaration {
   ///   the values are ``Schema`` objects describing them.
   ///   - requiredParameters: A list of required parameters by name.
   public init(name: String, description: String, parameters: [String: Schema]?,
-              requiredParameters: [String]?) {
+              requiredParameters: [String]? = nil) {
     self.name = name
     self.description = description
     self.parameters = Schema(