diff --git a/dlls/ntoskrnl.exe/ntoskrnl.c b/dlls/ntoskrnl.exe/ntoskrnl.c
index d7f57bad206..48e9656a156 100644
--- a/dlls/ntoskrnl.exe/ntoskrnl.c
+++ b/dlls/ntoskrnl.exe/ntoskrnl.c
@@ -3056,6 +3056,15 @@ HANDLE WINAPI PsGetCurrentThreadId(void)
 }
 
 
+/***********************************************************************
+ *           PsIsSystemThread   (NTOSKRNL.EXE.@)
+ */
+BOOLEAN WINAPI PsIsSystemThread(PETHREAD thread)
+{
+    return thread->kthread.process == PsInitialSystemProcess;
+}
+
+
 /***********************************************************************
  *           PsGetVersion   (NTOSKRNL.EXE.@)
  */
diff --git a/dlls/ntoskrnl.exe/ntoskrnl.exe.spec b/dlls/ntoskrnl.exe/ntoskrnl.exe.spec
index 7a802068a1a..26d7570e6af 100644
--- a/dlls/ntoskrnl.exe/ntoskrnl.exe.spec
+++ b/dlls/ntoskrnl.exe/ntoskrnl.exe.spec
@@ -908,7 +908,7 @@
 @ stdcall PsImpersonateClient(ptr ptr long long long)
 @ extern PsInitialSystemProcess
 @ stub PsIsProcessBeingDebugged
-@ stub PsIsSystemThread
+@ stdcall PsIsSystemThread(ptr)
 @ stub PsIsThreadImpersonating
 @ stub PsIsThreadTerminating
 @ stub PsJobType
diff --git a/dlls/ntoskrnl.exe/ntoskrnl_private.h b/dlls/ntoskrnl.exe/ntoskrnl_private.h
index e5805228b9b..126505694bd 100644
--- a/dlls/ntoskrnl.exe/ntoskrnl_private.h
+++ b/dlls/ntoskrnl.exe/ntoskrnl_private.h
@@ -39,6 +39,11 @@ struct _KTHREAD
     CLIENT_ID id;
 };
 
+struct _ETHREAD
+{
+    struct _KTHREAD kthread;
+};
+
 void *alloc_kernel_object( POBJECT_TYPE type, HANDLE handle, SIZE_T size, LONG ref ) DECLSPEC_HIDDEN;
 HANDLE kernel_object_handle( void *obj, unsigned int access ) DECLSPEC_HIDDEN;
 NTSTATUS kernel_object_from_handle( HANDLE handle, POBJECT_TYPE type, void **ret ) DECLSPEC_HIDDEN;
diff --git a/dlls/ntoskrnl.exe/tests/driver.c b/dlls/ntoskrnl.exe/tests/driver.c
index 8dbae9d8814..66fdcafa4a8 100644
--- a/dlls/ntoskrnl.exe/tests/driver.c
+++ b/dlls/ntoskrnl.exe/tests/driver.c
@@ -337,6 +337,8 @@ static void test_currentprocess(void)
     thread = PsGetCurrentThread();
     ret = wait_single( thread, 0 );
     ok(ret == STATUS_TIMEOUT, "got %#x\n", ret);
+
+    ok(!PsIsSystemThread((PETHREAD)KeGetCurrentThread()), "unexpected system thread\n");
 }
 
 static void sleep(void)
diff --git a/include/ddk/ntifs.h b/include/ddk/ntifs.h
index ec4d1d5aa7f..2c61329d9ec 100644
--- a/include/ddk/ntifs.h
+++ b/include/ddk/ntifs.h
@@ -131,6 +131,7 @@ typedef struct _FS_FILTER_CALLBACKS
 
 BOOLEAN WINAPI FsRtlIsNameInExpression(PUNICODE_STRING, PUNICODE_STRING, BOOLEAN, PWCH);
 NTSTATUS WINAPI ObQueryNameString(PVOID,POBJECT_NAME_INFORMATION,ULONG,PULONG);
+BOOLEAN WINAPI PsIsSystemThread(PETHREAD);
 NTSTATUS WINAPI PsLookupProcessByProcessId(HANDLE,PEPROCESS*);
 NTSTATUS WINAPI PsLookupThreadByThreadId(HANDLE,PETHREAD*);
 void WINAPI PsRevertToSelf(void);