diff --git a/cocoa/src/appkit.rs b/cocoa/src/appkit.rs
index 36bd2634..3541309a 100644
--- a/cocoa/src/appkit.rs
+++ b/cocoa/src/appkit.rs
@@ -679,12 +679,18 @@ pub trait NSRunningApplication: Sized {
             runningApplicationWithProcessIdentifier: pid
         ]
     }
+
+    unsafe fn processIdentifier(self) -> libc::pid_t;
 }
 
 impl NSRunningApplication for id {
     unsafe fn activateWithOptions_(self, options: NSApplicationActivationOptions) -> BOOL {
         msg_send![self, activateWithOptions: options as NSUInteger]
     }
+
+    unsafe fn processIdentifier(self) -> libc::pid_t {
+        msg_send![self, processIdentifier]
+    }
 }
 
 pub trait NSPasteboard: Sized {