diff --git a/dlls/winecoreaudio.drv/coreaudio.c b/dlls/winecoreaudio.drv/coreaudio.c
index f1ab4cf7986..56504a8b7b0 100644
--- a/dlls/winecoreaudio.drv/coreaudio.c
+++ b/dlls/winecoreaudio.drv/coreaudio.c
@@ -1115,6 +1115,18 @@ static NTSTATUS capture_resample(void *args)
     return STATUS_SUCCESS;
 }
 
+static NTSTATUS get_buffer_size(void *args)
+{
+    struct get_buffer_size_params *params = args;
+    struct coreaudio_stream *stream = params->stream;
+
+    OSSpinLockLock(&stream->lock);
+    *params->frames = stream->bufsize_frames;
+    OSSpinLockUnlock(&stream->lock);
+    params->result = S_OK;
+    return STATUS_SUCCESS;
+}
+
 unixlib_entry_t __wine_unix_call_funcs[] =
 {
     get_endpoint_ids,
@@ -1122,6 +1134,7 @@ unixlib_entry_t __wine_unix_call_funcs[] =
     release_stream,
     get_mix_format,
     is_format_supported,
+    get_buffer_size,
 
     capture_resample /* temporary */
 };
diff --git a/dlls/winecoreaudio.drv/mmdevdrv.c b/dlls/winecoreaudio.drv/mmdevdrv.c
index 578312bf4ef..cd33cababd1 100644
--- a/dlls/winecoreaudio.drv/mmdevdrv.c
+++ b/dlls/winecoreaudio.drv/mmdevdrv.c
@@ -855,6 +855,7 @@ static HRESULT WINAPI AudioClient_GetBufferSize(IAudioClient3 *iface,
         UINT32 *frames)
 {
     ACImpl *This = impl_from_IAudioClient3(iface);
+    struct get_buffer_size_params params;
 
     TRACE("(%p)->(%p)\n", This, frames);
 
@@ -864,13 +865,10 @@ static HRESULT WINAPI AudioClient_GetBufferSize(IAudioClient3 *iface,
     if(!This->stream)
         return AUDCLNT_E_NOT_INITIALIZED;
 
-    OSSpinLockLock(&This->stream->lock);
-
-    *frames = This->stream->bufsize_frames;
-
-    OSSpinLockUnlock(&This->stream->lock);
-
-    return S_OK;
+    params.stream = This->stream;
+    params.frames = frames;
+    UNIX_CALL(get_buffer_size, &params);
+    return params.result;
 }
 
 static HRESULT ca_get_max_stream_latency(ACImpl *This, UInt32 *max)
diff --git a/dlls/winecoreaudio.drv/unixlib.h b/dlls/winecoreaudio.drv/unixlib.h
index c1762c50e7e..7e08b347b02 100644
--- a/dlls/winecoreaudio.drv/unixlib.h
+++ b/dlls/winecoreaudio.drv/unixlib.h
@@ -93,6 +93,13 @@ struct is_format_supported_params
     HRESULT result;
 };
 
+struct get_buffer_size_params
+{
+    struct coreaudio_stream *stream;
+    HRESULT result;
+    UINT32 *frames;
+};
+
 enum unix_funcs
 {
     unix_get_endpoint_ids,
@@ -100,6 +107,7 @@ enum unix_funcs
     unix_release_stream,
     unix_get_mix_format,
     unix_is_format_supported,
+    unix_get_buffer_size,
 
     unix_capture_resample /* temporary */
 };