diff --git a/Sources/Core/File.swift b/Sources/Core/File.swift
index 9228252e..845b74f2 100644
--- a/Sources/Core/File.swift
+++ b/Sources/Core/File.swift
@@ -13,7 +13,13 @@ public struct File: Codable {
 
     /// The file extension, if it has one.
     public var ext: String? {
-        return filename.split(separator: ".").last.map(String.init)
+        let parts = filename.split(separator: ".")
+
+        if parts.count > 1 {
+            return parts.last.map(String.init)
+        } else {
+            return nil
+        }
     }
 
     /// Creates a new `File`.