diff --git a/SwiftGit2/Repository.swift b/SwiftGit2/Repository.swift
index 6449d14..332bd5d 100644
--- a/SwiftGit2/Repository.swift
+++ b/SwiftGit2/Repository.swift
@@ -15,8 +15,8 @@ public typealias CheckoutProgressBlock = (String?, Int, Int) -> Void
 /// Helper function used as the libgit2 progress callback in git_checkout_options.
 /// This is a function with a type signature of git_checkout_progress_cb.
 private func checkoutProgressCallback(path: UnsafePointer<Int8>?, completed_steps: Int, total_steps: Int, payload: UnsafeMutableRawPointer?) -> Void {
-	if (payload != nil) {
-		let buffer = payload!.assumingMemoryBound(to: CheckoutProgressBlock.self)
+	if let payload = payload {
+		let buffer = payload.assumingMemoryBound(to: CheckoutProgressBlock.self)
 		let block: CheckoutProgressBlock
 		if completed_steps < total_steps {
 			block = buffer.pointee