diff --git a/dlls/ntdll/ntdll.spec b/dlls/ntdll/ntdll.spec
index 38ffad3a2cf..e2f5117972e 100644
--- a/dlls/ntdll/ntdll.spec
+++ b/dlls/ntdll/ntdll.spec
@@ -735,7 +735,7 @@
 # @ stub RtlIpv6AddressToStringW
 # @ stub RtlIpv6StringToAddressA
 # @ stub RtlIpv6StringToAddressExA
-# @ stub RtlIpv6StringToAddressExW
+@ stdcall RtlIpv6StringToAddressExW(wstr ptr ptr ptr)
 # @ stub RtlIpv6StringToAddressW
 @ stdcall RtlIsActivationContextActive(ptr)
 @ stdcall RtlIsCriticalSectionLocked(ptr)
diff --git a/dlls/ntdll/rtl.c b/dlls/ntdll/rtl.c
index 8ade7525f0e..1311604aafd 100644
--- a/dlls/ntdll/rtl.c
+++ b/dlls/ntdll/rtl.c
@@ -45,6 +45,7 @@
 #include "wine/unicode.h"
 #include "ntdll_misc.h"
 #include "inaddr.h"
+#include "in6addr.h"
 #include "ddk/ntddk.h"
 
 WINE_DEFAULT_DEBUG_CHANNEL(ntdll);
@@ -902,6 +903,15 @@ NTSTATUS WINAPI RtlIpv4StringToAddressW(const WCHAR *str, BOOLEAN strict, const
     return STATUS_NOT_IMPLEMENTED;
 }
 
+/***********************************************************************
+ * RtlIpv6StringToAddressExW [NTDLL.@]
+ */
+NTSTATUS NTAPI RtlIpv6StringToAddressExW(const WCHAR *str, IN6_ADDR *address, ULONG *scope, USHORT *port)
+{
+    FIXME("(%s, %p, %p, %p): stub\n", debugstr_w(str), address, scope, port);
+    return STATUS_NOT_IMPLEMENTED;
+}
+
 /***********************************************************************
  * RtlIpv4AddressToStringExW [NTDLL.@]
  *
diff --git a/dlls/ntoskrnl.exe/ntoskrnl.exe.spec b/dlls/ntoskrnl.exe/ntoskrnl.exe.spec
index 46c03eca3b9..137f5189298 100644
--- a/dlls/ntoskrnl.exe/ntoskrnl.exe.spec
+++ b/dlls/ntoskrnl.exe/ntoskrnl.exe.spec
@@ -1096,7 +1096,7 @@
 @ stub RtlIpv6AddressToStringW
 @ stub RtlIpv6StringToAddressA
 @ stub RtlIpv6StringToAddressExA
-@ stub RtlIpv6StringToAddressExW
+@ stdcall RtlIpv6StringToAddressExW(wstr ptr ptr ptr)
 @ stub RtlIpv6StringToAddressW
 @ stub RtlIsGenericTableEmpty
 @ stub RtlIsGenericTableEmptyAvl