diff --git a/dlls/ntoskrnl.exe/ntoskrnl.c b/dlls/ntoskrnl.exe/ntoskrnl.c
index e94feabc826..4092e33db43 100644
--- a/dlls/ntoskrnl.exe/ntoskrnl.c
+++ b/dlls/ntoskrnl.exe/ntoskrnl.c
@@ -3145,6 +3145,15 @@ BOOLEAN WINAPI MmIsThisAnNtAsSystem(void)
     return FALSE;
 }
 
+/***********************************************************************
+ *           MmProtectMdlSystemAddress   (NTOSKRNL.EXE.@)
+ */
+NTSTATUS WINAPI MmProtectMdlSystemAddress(PMDL MemoryDescriptorList, ULONG NewProtect)
+{
+    FIXME("(%p, %u) stub\n", MemoryDescriptorList, NewProtect);
+    return STATUS_SUCCESS;
+}
+
 /***********************************************************************
  *           MmQuerySystemSize   (NTOSKRNL.EXE.@)
  */
diff --git a/dlls/ntoskrnl.exe/ntoskrnl.exe.spec b/dlls/ntoskrnl.exe/ntoskrnl.exe.spec
index 8892fde5054..6ac70c718f1 100644
--- a/dlls/ntoskrnl.exe/ntoskrnl.exe.spec
+++ b/dlls/ntoskrnl.exe/ntoskrnl.exe.spec
@@ -733,7 +733,7 @@
 @ stdcall MmProbeAndLockPages(ptr long long)
 @ stub MmProbeAndLockProcessPages
 @ stub MmProbeAndLockSelectedPages
-@ stub MmProtectMdlSystemAddress
+@ stdcall MmProtectMdlSystemAddress(ptr long)
 @ stdcall MmQuerySystemSize()
 @ stub MmRemovePhysicalMemory
 @ stdcall MmResetDriverPaging(ptr)