diff --git a/include/mutex b/include/mutex
index c87d0fd..21d3834 100644
--- a/include/mutex
+++ b/include/mutex
@@ -364,9 +364,9 @@
 
 #ifndef _LIBCPP_HAS_NO_VARIADICS
 
-template <class _L0, class _L1, class ..._L2>
+template <class _L0, class _L1, class _L2, class ..._L3>
 void
-__lock_first(int __i, _L0& __l0, _L1& __l1, _L2& ...__l2)
+__lock_first(int __i, _L0& __l0, _L1& __l1, _L2& __l2, _L3& ...__l3)
 {
     while (true)
     {
@@ -375,7 +375,7 @@
         case 0:
             {
                 unique_lock<_L0> __u0(__l0);
-                __i = try_lock(__l1, __l2...);
+                __i = try_lock(__l1, __l2, __l3...);
                 if (__i == -1)
                 {
                     __u0.release();
@@ -388,32 +388,32 @@
         case 1:
             {
                 unique_lock<_L1> __u1(__l1);
-                __i = try_lock(__l2..., __l0);
+                __i = try_lock(__l2, __l3..., __l0);
                 if (__i == -1)
                 {
                     __u1.release();
                     return;
                 }
             }
-            if (__i == sizeof...(_L2))
+            if (__i == sizeof...(_L3) + 1)
                 __i = 0;
             else
                 __i += 2;
             sched_yield();
             break;
         default:
-            __lock_first(__i - 2, __l2..., __l0, __l1);
+            __lock_first(__i - 2, __l2, __l3..., __l0, __l1);
             return;
         }
     }
 }
 
-template <class _L0, class _L1, class ..._L2>
+template <class _L0, class _L1, class _L2, class ..._L3>
 inline _LIBCPP_INLINE_VISIBILITY
 void
-lock(_L0& __l0, _L1& __l1, _L2& ...__l2)
+lock(_L0& __l0, _L1& __l1, _L2& __l2, _L3& ...__l3)
 {
-    __lock_first(0, __l0, __l1, __l2...);
+    __lock_first(0, __l0, __l1, __l2, __l3...);
 }
 
 #endif  // _LIBCPP_HAS_NO_VARIADICS