diff --git a/Sources/AXPropertyDelegate.swift b/Sources/AXPropertyDelegate.swift
index 05fc8b8..e74a6d8 100644
--- a/Sources/AXPropertyDelegate.swift
+++ b/Sources/AXPropertyDelegate.swift
@@ -1,6 +1,7 @@
 import Foundation
 import AXSwift
 import PromiseKit
+import AppKit
 
 /// Implements PropertyDelegate using the AXUIElement API.
 class AXPropertyDelegate<T: Equatable, UIElement: UIElementType>: PropertyDelegate {
diff --git a/Sources/Application.swift b/Sources/Application.swift
index a018474..90fc023 100644
--- a/Sources/Application.swift
+++ b/Sources/Application.swift
@@ -112,10 +112,10 @@ final class OSXApplicationDelegate<
     var isHidden: WriteableProperty<OfType<Bool>>!
 
     var processIdentifier: pid_t!
-    lazy var runningApplication: NSRunningApplication =
-        NSRunningApplication(processIdentifier: self.processIdentifier)!
+    lazy var runningApplication: NSRunningApplication? =
+        NSRunningApplication(processIdentifier: self.processIdentifier)
     lazy var bundleIdentifier: String? =
-        self.runningApplication.bundleIdentifier
+        self.runningApplication?.bundleIdentifier
 
     var knownWindows: [WindowDelegate] {
         return windows.map({ $0 as WindowDelegate })