diff --git a/osdep/mac/input_helper.swift b/osdep/mac/input_helper.swift
index 0acec6bd40..0ec5837864 100644
--- a/osdep/mac/input_helper.swift
+++ b/osdep/mac/input_helper.swift
@@ -18,6 +18,14 @@
 import Cocoa
 import Carbon.HIToolbox
 
+extension NSCondition {
+    fileprivate func withLock<T>(_ body: () throws -> T) rethrows -> T {
+        self.lock()
+        defer { self.unlock() }
+        return try body()
+    }
+}
+
 class InputHelper: NSObject {
     var option: OptionHelper?
     var lock = NSCondition()