diff --git a/dlls/mfplat/buffer.c b/dlls/mfplat/buffer.c
index a912c61a3ac..1cb84cba944 100644
--- a/dlls/mfplat/buffer.c
+++ b/dlls/mfplat/buffer.c
@@ -18,6 +18,8 @@
 
 #define COBJMACROS
 
+#include <malloc.h>
+
 #include "mfplat_private.h"
 #include "rtworkq.h"
 
@@ -171,7 +173,7 @@ static ULONG WINAPI memory_buffer_Release(IMFMediaBuffer *iface)
         }
         DeleteCriticalSection(&buffer->cs);
         free(buffer->_2d.linear_buffer);
-        free(buffer->data);
+        _aligned_free(buffer->data);
         free(buffer);
     }
 
@@ -1254,8 +1256,26 @@ static const IMFDXGIBufferVtbl dxgi_buffer_vtbl =
 static HRESULT memory_buffer_init(struct buffer *buffer, DWORD max_length, DWORD alignment,
         const IMFMediaBufferVtbl *vtbl)
 {
-    if (!(buffer->data = calloc(1, ALIGN_SIZE(max_length, alignment))))
+    size_t size;
+
+    if (!alignment) alignment = MF_64_BYTE_ALIGNMENT;
+    alignment++;
+
+    if (alignment & (alignment - 1))
+    {
+        alignment--;
+        alignment |= alignment >> 1;
+        alignment |= alignment >> 2;
+        alignment |= alignment >> 4;
+        alignment |= alignment >> 8;
+        alignment |= alignment >> 16;
+        alignment++;
+    }
+
+    size = ALIGN_SIZE(max_length, alignment - 1);
+    if (!(buffer->data = _aligned_malloc(size, alignment)))
         return E_OUTOFMEMORY;
+    memset(buffer->data, 0, size);
 
     buffer->IMFMediaBuffer_iface.lpVtbl = vtbl;
     buffer->refcount = 1;
diff --git a/dlls/mfplat/tests/mfplat.c b/dlls/mfplat/tests/mfplat.c
index f61dbad7ab9..d9c25edaa72 100644
--- a/dlls/mfplat/tests/mfplat.c
+++ b/dlls/mfplat/tests/mfplat.c
@@ -2287,8 +2287,25 @@ static void test_system_memory_buffer(void)
     ok(hr == S_OK, "Unexpected hr %#lx.\n", hr);
 
     IMFMediaBuffer_Release(buffer);
+}
+
+static void test_system_memory_aligned_buffer(void)
+{
+    static const DWORD alignments[] =
+    {
+        MF_16_BYTE_ALIGNMENT,
+        MF_32_BYTE_ALIGNMENT,
+        MF_64_BYTE_ALIGNMENT,
+        MF_128_BYTE_ALIGNMENT,
+        MF_256_BYTE_ALIGNMENT,
+        MF_512_BYTE_ALIGNMENT,
+    };
+    IMFMediaBuffer *buffer;
+    DWORD length, max;
+    unsigned int i;
+    BYTE *data;
+    HRESULT hr;
 
-    /* Aligned buffer. */
     hr = MFCreateAlignedMemoryBuffer(16, MF_8_BYTE_ALIGNMENT, NULL);
     ok(FAILED(hr), "Unexpected hr %#lx.\n", hr);
 
@@ -2324,6 +2341,25 @@ static void test_system_memory_buffer(void)
     ok(hr == S_OK, "Failed to unlock, hr %#lx.\n", hr);
 
     IMFMediaBuffer_Release(buffer);
+
+    for (i = 0; i < ARRAY_SIZE(alignments); ++i)
+    {
+        hr = MFCreateAlignedMemoryBuffer(200, alignments[i], &buffer);
+        ok(hr == S_OK, "Failed to create memory buffer, hr %#lx.\n", hr);
+
+        hr = IMFMediaBuffer_Lock(buffer, &data, &max, &length);
+        ok(hr == S_OK, "Failed to lock, hr %#lx.\n", hr);
+        ok(max == 200 && !length, "Unexpected length.\n");
+        ok(!((uintptr_t)data & alignments[i]), "Data at %p is misaligned.\n", data);
+        hr = IMFMediaBuffer_Unlock(buffer);
+        ok(hr == S_OK, "Failed to unlock, hr %#lx.\n", hr);
+
+        IMFMediaBuffer_Release(buffer);
+    }
+
+    hr = MFCreateAlignedMemoryBuffer(200, 0, &buffer);
+    ok(hr == S_OK, "Failed to create memory buffer, hr %#lx.\n", hr);
+    IMFMediaBuffer_Release(buffer);
 }
 
 static void test_sample(void)
@@ -7980,6 +8016,7 @@ START_TEST(mfplat)
     test_file_stream();
     test_MFCreateMFByteStreamOnStream();
     test_system_memory_buffer();
+    test_system_memory_aligned_buffer();
     test_source_resolver();
     test_MFCreateAsyncResult();
     test_allocate_queue();