diff --git a/dll/ntdll/def/ntdll.spec b/dll/ntdll/def/ntdll.spec
index 3db2bf08b82..363ed834289 100644
--- a/dll/ntdll/def/ntdll.spec
+++ b/dll/ntdll/def/ntdll.spec
@@ -728,7 +728,7 @@
 @ stdcall RtlCreateSecurityDescriptor(ptr long)
 @ stdcall RtlCreateServiceSid(ptr ptr ptr) # Exists in Windows 2003 SP 2
 @ stdcall RtlCreateSystemVolumeInformationFolder(ptr)
-@ stdcall RtlCreateTagHeap(ptr long str str)
+@ stdcall RtlCreateTagHeap(ptr long wstr wstr)
 @ stdcall RtlCreateTimer(ptr ptr ptr ptr long long long)
 @ stdcall RtlCreateTimerQueue(ptr)
 @ stdcall RtlCreateUnicodeString(ptr wstr)
diff --git a/sdk/include/ndk/rtlfuncs.h b/sdk/include/ndk/rtlfuncs.h
index a99ba39fa0e..ffc3bb1bcae 100644
--- a/sdk/include/ndk/rtlfuncs.h
+++ b/sdk/include/ndk/rtlfuncs.h
@@ -861,7 +861,7 @@ NTAPI
 RtlCreateTagHeap(
     _In_ HANDLE HeapHandle,
     _In_ ULONG Flags,
-    _In_ PWSTR TagName,
+    _In_opt_ PWSTR TagName,
     _In_ PWSTR TagSubName
 );
 
diff --git a/sdk/lib/rtl/heap.c b/sdk/lib/rtl/heap.c
index 019a4f80216..847051df44c 100644
--- a/sdk/lib/rtl/heap.c
+++ b/sdk/lib/rtl/heap.c
@@ -4028,10 +4028,10 @@ RtlExtendHeap(IN HANDLE Heap,
 
 ULONG
 NTAPI
-RtlCreateTagHeap(IN HANDLE HeapHandle,
-                 IN ULONG Flags,
-                 IN PWSTR TagName,
-                 IN PWSTR TagSubName)
+RtlCreateTagHeap(_In_ HANDLE HeapHandle,
+                 _In_ ULONG Flags,
+                 _In_opt_ PWSTR TagName,
+                 _In_ PWSTR TagSubName)
 {
     /* TODO */
     UNIMPLEMENTED;