diff --git a/dlls/qcap/audiorecord.c b/dlls/qcap/audiorecord.c
index 291ca4452b3..5ece56e97ec 100644
--- a/dlls/qcap/audiorecord.c
+++ b/dlls/qcap/audiorecord.c
@@ -46,6 +46,7 @@ struct audio_record
     CRITICAL_SECTION state_cs;
 
     AM_MEDIA_TYPE format;
+    ALLOCATOR_PROPERTIES props;
 };
 
 static struct audio_record *impl_from_strmbase_filter(struct strmbase_filter *filter)
@@ -158,12 +159,18 @@ static HRESULT WINAPI audio_record_source_DecideBufferSize(struct strmbase_sourc
     MMRESULT ret;
     HRESULT hr;
 
-    props->cBuffers = 4;
+    props->cBuffers = (filter->props.cBuffers == -1) ? 4 : filter->props.cBuffers;
     /* This is the algorithm that native uses. The alignment to an even number
      * doesn't make much sense, and may be a bug. */
-    props->cbBuffer = (format->nAvgBytesPerSec / 2) & ~1;
-    props->cbAlign = 1;
-    props->cbPrefix = 0;
+    if (filter->props.cbBuffer == -1)
+        props->cbBuffer = (format->nAvgBytesPerSec / 2) & ~1;
+    else
+        props->cbBuffer = filter->props.cbBuffer & ~1;
+    if (filter->props.cbAlign == -1 || filter->props.cbAlign == 0)
+        props->cbAlign = 1;
+    else
+        props->cbAlign = filter->props.cbAlign;
+    props->cbPrefix = (filter->props.cbPrefix == -1) ? 0 : filter->props.cbPrefix;
 
     if (FAILED(hr = IMemAllocator_SetProperties(allocator, props, &ret_props)))
         return hr;
@@ -356,10 +363,17 @@ static ULONG WINAPI buffer_negotiation_Release(IAMBufferNegotiation *iface)
 static HRESULT WINAPI buffer_negotiation_SuggestAllocatorProperties(
         IAMBufferNegotiation *iface, const ALLOCATOR_PROPERTIES *props)
 {
-    FIXME("iface %p, props %p, stub!\n", iface, props);
+    struct audio_record *filter = impl_from_IAMBufferNegotiation(iface);
+
+    TRACE("filter %p, props %p.\n", filter, props);
     TRACE("Requested %ld buffers, size %ld, alignment %ld, prefix %ld.\n",
             props->cBuffers, props->cbBuffer, props->cbAlign, props->cbPrefix);
-    return E_NOTIMPL;
+
+    EnterCriticalSection(&filter->state_cs);
+    filter->props = *props;
+    LeaveCriticalSection(&filter->state_cs);
+
+    return S_OK;
 }
 
 static HRESULT WINAPI buffer_negotiation_GetAllocatorProperties(
@@ -788,6 +802,11 @@ HRESULT audio_record_create(IUnknown *outer, IUnknown **out)
         return hr;
     }
 
+    object->props.cBuffers = -1;
+    object->props.cbBuffer = -1;
+    object->props.cbAlign = -1;
+    object->props.cbPrefix = -1;
+
     object->IPersistPropertyBag_iface.lpVtbl = &PersistPropertyBagVtbl;
     strmbase_filter_init(&object->filter, outer, &CLSID_AudioRecord, &filter_ops);
 
diff --git a/dlls/qcap/tests/audiorecord.c b/dlls/qcap/tests/audiorecord.c
index a5669612351..ed6c54648d0 100644
--- a/dlls/qcap/tests/audiorecord.c
+++ b/dlls/qcap/tests/audiorecord.c
@@ -618,6 +618,7 @@ static void test_source_allocator(IFilterGraph2 *graph, IMediaControl *control,
         IPin *source, struct testfilter *testsink)
 {
     ALLOCATOR_PROPERTIES props, req_props = {2, 3200, 32, 0};
+    IAMBufferNegotiation *negotiation;
     IMemAllocator *allocator;
     IMediaSample *sample;
     WAVEFORMATEX format;
@@ -692,6 +693,56 @@ static void test_source_allocator(IFilterGraph2 *graph, IMediaControl *control,
 
     IFilterGraph2_Disconnect(graph, source);
     IFilterGraph2_Disconnect(graph, &testsink->sink.pin.IPin_iface);
+
+    /* Test IAMBufferNegotiation. *This* is respected. */
+
+    IPin_QueryInterface(source, &IID_IAMBufferNegotiation, (void **)&negotiation);
+
+    hr = IAMBufferNegotiation_SuggestAllocatorProperties(negotiation, &req_props);
+    ok(hr == S_OK, "Got hr %#lx.\n", hr);
+
+    init_pcm_mt(&mt, &format, 1, 32000, 16);
+    hr = IFilterGraph2_ConnectDirect(graph, source, &testsink->sink.pin.IPin_iface, &mt);
+    ok(hr == S_OK, "Got hr %#lx.\n", hr);
+
+    todo_wine ok(testsink->sink.pAllocator && testsink->sink.pAllocator != allocator,
+            "Got unexpected allocator %p.\n", testsink->sink.pAllocator);
+    hr = IMemAllocator_GetProperties(testsink->sink.pAllocator, &props);
+    ok(hr == S_OK, "Got hr %#lx.\n", hr);
+    ok(props.cBuffers == req_props.cBuffers, "Got %ld buffers.\n", props.cBuffers);
+    ok(props.cbBuffer == req_props.cbBuffer, "Got size %ld.\n", props.cbBuffer);
+    ok(props.cbAlign == req_props.cbAlign, "Got alignment %ld.\n", props.cbAlign);
+    ok(props.cbPrefix == req_props.cbPrefix, "Got prefix %ld.\n", props.cbPrefix);
+
+    IFilterGraph2_Disconnect(graph, source);
+    IFilterGraph2_Disconnect(graph, &testsink->sink.pin.IPin_iface);
+
+    for (req_props.cbBuffer = 32000; req_props.cbBuffer < 32050; ++req_props.cbBuffer)
+    {
+        req_props.cBuffers = -1;
+        req_props.cbAlign = 0;
+        hr = IAMBufferNegotiation_SuggestAllocatorProperties(negotiation, &req_props);
+        ok(hr == S_OK, "Got hr %#lx.\n", hr);
+
+        init_pcm_mt(&mt, &format, 1, 32000, 8);
+        hr = IFilterGraph2_ConnectDirect(graph, source, &testsink->sink.pin.IPin_iface, &mt);
+        ok(hr == S_OK, "Got hr %#lx.\n", hr);
+
+        todo_wine ok(testsink->sink.pAllocator && testsink->sink.pAllocator != allocator,
+                "Got unexpected allocator %p.\n", testsink->sink.pAllocator);
+        hr = IMemAllocator_GetProperties(testsink->sink.pAllocator, &props);
+        ok(hr == S_OK, "Got hr %#lx.\n", hr);
+        ok(props.cBuffers == 4, "Got %ld buffers.\n", props.cBuffers);
+        ok(props.cbBuffer == (req_props.cbBuffer & ~1),
+                "Got size %ld for %ld.\n", props.cbBuffer, req_props.cbBuffer);
+        ok(props.cbAlign == 1, "Got alignment %ld.\n", props.cbAlign);
+        ok(props.cbPrefix == req_props.cbPrefix, "Got prefix %ld.\n", props.cbPrefix);
+
+        IFilterGraph2_Disconnect(graph, source);
+        IFilterGraph2_Disconnect(graph, &testsink->sink.pin.IPin_iface);
+    }
+
+    IAMBufferNegotiation_Release(negotiation);
 }
 
 static void test_filter_state(IFilterGraph2 *graph, IMediaControl *control,