diff --git a/rtl/darwin/pthread.inc b/rtl/darwin/pthread.inc
index 7420818dcb..e0fe6ffd55 100644
--- a/rtl/darwin/pthread.inc
+++ b/rtl/darwin/pthread.inc
@@ -55,6 +55,7 @@ function  pthread_self:pthread_t; cdecl;external 'c';
 function  pthread_mutex_init (p:ppthread_mutex_t;o:ppthread_mutexattr_t):cint; cdecl;external 'c';
 function  pthread_mutex_destroy (p:ppthread_mutex_t):cint; cdecl;external 'c';
 function  pthread_mutex_lock    (p:ppthread_mutex_t):cint; cdecl;external 'c';
+function  pthread_mutex_trylock (p:ppthread_mutex_t):cint; cdecl;external 'c';
 function  pthread_mutex_unlock  (p:ppthread_mutex_t):cint; cdecl;external 'c';
 function  pthread_cancel(_para1:pthread_t):cint;cdecl;external 'c';
 function  pthread_detach(_para1:pthread_t):cint;cdecl;external 'c';