diff --git a/dlls/ole32/filemoniker.c b/dlls/ole32/filemoniker.c
index f52881108c7..213971ea96b 100644
--- a/dlls/ole32/filemoniker.c
+++ b/dlls/ole32/filemoniker.c
@@ -608,21 +608,16 @@ FileMonikerImpl_BindToStorage(IMoniker* iface, IBindCtx* pbc, IMoniker* pmkToLef
     return E_NOTIMPL;
 }
 
-/******************************************************************************
- *        FileMoniker_Reduce
- ******************************************************************************/
-static HRESULT WINAPI
-FileMonikerImpl_Reduce(IMoniker* iface, IBindCtx* pbc, DWORD dwReduceHowFar,
-                       IMoniker** ppmkToLeft, IMoniker** ppmkReduced)
+static HRESULT WINAPI FileMonikerImpl_Reduce(IMoniker *iface, IBindCtx *pbc, DWORD howfar,
+        IMoniker **toleft, IMoniker **reduced)
 {
-    TRACE("(%p,%p,%d,%p,%p)\n",iface,pbc,dwReduceHowFar,ppmkToLeft,ppmkReduced);
+    TRACE("%p, %p, %d, %p, %p.\n", iface, pbc, howfar, toleft, reduced);
 
-    if (ppmkReduced==NULL)
-        return E_POINTER;
+    if (!pbc || !reduced)
+        return E_INVALIDARG;
 
     IMoniker_AddRef(iface);
-
-    *ppmkReduced=iface;
+    *reduced = iface;
 
     return MK_S_REDUCED_TO_SELF;
 }
diff --git a/dlls/ole32/tests/moniker.c b/dlls/ole32/tests/moniker.c
index 91382da6a02..2c257dcff50 100644
--- a/dlls/ole32/tests/moniker.c
+++ b/dlls/ole32/tests/moniker.c
@@ -2098,7 +2098,7 @@ todo_wine
 
 static void test_file_moniker(WCHAR* path)
 {
-    IMoniker *moniker1 = NULL, *moniker2 = NULL, *inverse, *reduced, *anti;
+    IMoniker *moniker1 = NULL, *moniker2 = NULL, *m3, *inverse, *reduced, *anti;
     IEnumMoniker *enummoniker;
     IBindCtx *bind_ctx;
     IStream *stream;
@@ -2142,9 +2142,19 @@ static void test_file_moniker(WCHAR* path)
     ok(hr == S_OK, "Failed to create bind context, hr %#x.\n", hr);
 
     hr = IMoniker_Reduce(moniker1, NULL, MKRREDUCE_ALL, NULL, &reduced);
-todo_wine
     ok(hr == E_INVALIDARG, "Unexpected hr %#x.\n", hr);
 
+    hr = IMoniker_Reduce(moniker1, bind_ctx, MKRREDUCE_ALL, NULL, NULL);
+    ok(hr == E_INVALIDARG, "Unexpected hr %#x.\n", hr);
+
+    m3 = anti = create_antimoniker(1);
+    hr = IMoniker_Reduce(moniker1, bind_ctx, MKRREDUCE_ALL, &m3, &reduced);
+    ok(hr == MK_S_REDUCED_TO_SELF, "Unexpected hr %#x.\n", hr);
+    ok(reduced == moniker1, "Unexpected moniker.\n");
+    ok(m3 == anti, "Unexpected pointer.\n");
+    IMoniker_Release(reduced);
+    IMoniker_Release(anti);
+
     hr = IMoniker_Reduce(moniker1, bind_ctx, MKRREDUCE_ALL, NULL, &reduced);
     ok(hr == MK_S_REDUCED_TO_SELF, "Unexpected hr %#x.\n", hr);
     ok(reduced == moniker1, "Unexpected moniker.\n");