diff --git a/dlls/ntoskrnl.exe/ntoskrnl.c b/dlls/ntoskrnl.exe/ntoskrnl.c
index 40c18d8043e..6488e52cc9c 100644
--- a/dlls/ntoskrnl.exe/ntoskrnl.c
+++ b/dlls/ntoskrnl.exe/ntoskrnl.c
@@ -2971,6 +2971,14 @@ PVOID WINAPI MmGetSystemRoutineAddress(PUNICODE_STRING SystemRoutineName)
     return pFunc;
 }
 
+/***********************************************************************
+ *           MmIsThisAnNtAsSystem   (NTOSKRNL.EXE.@)
+ */
+BOOLEAN WINAPI MmIsThisAnNtAsSystem(void)
+{
+    TRACE("\n");
+    return FALSE;
+}
 
 /***********************************************************************
  *           MmQuerySystemSize   (NTOSKRNL.EXE.@)
diff --git a/dlls/ntoskrnl.exe/ntoskrnl.exe.spec b/dlls/ntoskrnl.exe/ntoskrnl.exe.spec
index 359e2d9e69b..a3704a51ad9 100644
--- a/dlls/ntoskrnl.exe/ntoskrnl.exe.spec
+++ b/dlls/ntoskrnl.exe/ntoskrnl.exe.spec
@@ -699,7 +699,7 @@
 @ stub MmIsDriverVerifying
 @ stub MmIsNonPagedSystemAddressValid
 @ stub MmIsRecursiveIoFault
-@ stub MmIsThisAnNtAsSystem
+@ stdcall MmIsThisAnNtAsSystem()
 @ stub MmIsVerifierEnabled
 @ stub MmLockPagableDataSection
 @ stub MmLockPagableImageSection