diff --git a/dll/ntdll/nt_0600/ntdll_vista.spec b/dll/ntdll/nt_0600/ntdll_vista.spec
index d690a00983c..2eaebb54fcc 100644
--- a/dll/ntdll/nt_0600/ntdll_vista.spec
+++ b/dll/ntdll/nt_0600/ntdll_vista.spec
@@ -11,6 +11,7 @@
 @ stdcall RtlReleaseSRWLockShared(ptr)
 @ stdcall RtlAcquireSRWLockExclusive(ptr)
 @ stdcall RtlReleaseSRWLockExclusive(ptr)
+@ stdcall RtlTryAcquireSRWLockExclusive(ptr)
 @ stdcall RtlRunOnceInitialize(ptr)
 @ stdcall RtlRunOnceBeginInitialize(ptr long ptr)
 @ stdcall RtlRunOnceComplete(ptr long ptr)