diff --git a/dlls/kernel/process.c b/dlls/kernel/process.c
index e00cae29ab3..0f457fd1f97 100644
--- a/dlls/kernel/process.c
+++ b/dlls/kernel/process.c
@@ -2740,9 +2740,11 @@ BOOL WINAPI WriteProcessMemory( HANDLE process, LPVOID addr, LPCVOID buffer, SIZ
  */
 BOOL WINAPI FlushInstructionCache(HANDLE hProcess, LPCVOID lpBaseAddress, SIZE_T dwSize)
 {
+    NTSTATUS status;
     if (GetVersion() & 0x80000000) return TRUE; /* not NT, always TRUE */
-    FIXME("(%p,%p,0x%08lx): stub\n",hProcess, lpBaseAddress, dwSize);
-    return TRUE;
+    status = NtFlushInstructionCache( hProcess, lpBaseAddress, dwSize );
+    if (status) SetLastError( RtlNtStatusToDosError(status) );
+    return !status;
 }
 
 
diff --git a/dlls/ntdll/ntdll.spec b/dlls/ntdll/ntdll.spec
index 146d27149d3..50b29c69a89 100644
--- a/dlls/ntdll/ntdll.spec
+++ b/dlls/ntdll/ntdll.spec
@@ -115,7 +115,7 @@
 @ stdcall NtEnumerateValueKey (long long long long long long)
 @ stub NtExtendSection
 @ stdcall NtFlushBuffersFile(long ptr)
-@ stub NtFlushInstructionCache
+@ stdcall NtFlushInstructionCache(long ptr long)
 @ stdcall NtFlushKey(long)
 @ stdcall NtFlushVirtualMemory(long ptr ptr long)
 @ stub NtFlushWriteBuffer
@@ -698,7 +698,7 @@
 @ stdcall ZwEnumerateValueKey(long long long ptr long ptr) NtEnumerateValueKey
 @ stub ZwExtendSection
 @ stdcall ZwFlushBuffersFile(long ptr) NtFlushBuffersFile
-@ stub ZwFlushInstructionCache
+@ stdcall ZwFlushInstructionCache(long ptr long) NtFlushInstructionCache
 @ stdcall ZwFlushKey(long) NtFlushKey
 @ stdcall ZwFlushVirtualMemory(long ptr ptr long) NtFlushVirtualMemory
 @ stub ZwFlushWriteBuffer
diff --git a/dlls/ntdll/process.c b/dlls/ntdll/process.c
index c0c240e0cbf..c786ed6ad67 100644
--- a/dlls/ntdll/process.c
+++ b/dlls/ntdll/process.c
@@ -154,3 +154,20 @@ NTSTATUS WINAPI NtSetInformationProcess(
           ProcessHandle,ProcessInformationClass,ProcessInformation,ProcessInformationLength);
     return 0;
 }
+
+/******************************************************************************
+ * NtFlushInstructionCache [NTDLL.@]
+ * ZwFlushInstructionCache [NTDLL.@]
+ */
+NTSTATUS WINAPI NtFlushInstructionCache(
+        IN HANDLE ProcessHandle,
+        IN LPCVOID BaseAddress,
+        IN ULONG Size)
+{
+#ifdef __i386__
+    TRACE("%p %p %ld - no-op on x86\n", ProcessHandle, BaseAddress, Size );
+#else
+    FIXME("%p %p %ld\n", ProcessHandle, BaseAddress, Size );
+#endif
+    return STATUS_SUCCESS;
+}
diff --git a/include/winternl.h b/include/winternl.h
index aa90a757a6f..776d588e33c 100644
--- a/include/winternl.h
+++ b/include/winternl.h
@@ -1242,6 +1242,7 @@ NTSTATUS  WINAPI NtDuplicateObject(HANDLE,HANDLE,HANDLE,PHANDLE,ACCESS_MASK,ULON
 NTSTATUS  WINAPI NtEnumerateKey(HKEY,ULONG,KEY_INFORMATION_CLASS,void *,DWORD,DWORD *);
 NTSTATUS  WINAPI NtEnumerateValueKey(HKEY,ULONG,KEY_VALUE_INFORMATION_CLASS,PVOID,ULONG,PULONG);
 NTSTATUS  WINAPI NtFlushBuffersFile(HANDLE,IO_STATUS_BLOCK*);
+NTSTATUS  WINAPI NtFlushInstructionCache(HANDLE,LPCVOID,ULONG);
 NTSTATUS  WINAPI NtFlushKey(HKEY);
 NTSTATUS  WINAPI NtFlushVirtualMemory(HANDLE,LPCVOID*,ULONG*,ULONG);
 NTSTATUS  WINAPI NtFreeVirtualMemory(HANDLE,PVOID*,ULONG*,ULONG);