diff --git a/dlls/wineoss.drv/mmdevdrv.c b/dlls/wineoss.drv/mmdevdrv.c
index 80bac1d9ceb..c101d757836 100644
--- a/dlls/wineoss.drv/mmdevdrv.c
+++ b/dlls/wineoss.drv/mmdevdrv.c
@@ -1364,20 +1364,18 @@ static HRESULT WINAPI AudioCaptureClient_GetNextPacketSize(
         IAudioCaptureClient *iface, UINT32 *frames)
 {
     ACImpl *This = impl_from_IAudioCaptureClient(iface);
-    struct oss_stream *stream = This->stream;
+    struct get_next_packet_size_params params;
 
     TRACE("(%p)->(%p)\n", This, frames);
 
     if(!frames)
         return E_POINTER;
 
-    oss_lock(stream);
+    params.stream = This->stream;
+    params.frames = frames;
+    OSS_CALL(get_next_packet_size, &params);
 
-    *frames = stream->held_frames < stream->period_frames ? 0 : stream->period_frames;
-
-    oss_unlock(stream);
-
-    return S_OK;
+    return params.result;
 }
 
 static const IAudioCaptureClientVtbl AudioCaptureClient_Vtbl =
diff --git a/dlls/wineoss.drv/oss.c b/dlls/wineoss.drv/oss.c
index f1994295618..ffea1bb8338 100644
--- a/dlls/wineoss.drv/oss.c
+++ b/dlls/wineoss.drv/oss.c
@@ -1243,6 +1243,19 @@ static NTSTATUS get_current_padding(void *args)
     return oss_unlock_result(stream, &params->result, S_OK);
 }
 
+static NTSTATUS get_next_packet_size(void *args)
+{
+    struct get_next_packet_size_params *params = args;
+    struct oss_stream *stream = params->stream;
+    UINT32 *frames = params->frames;
+
+    oss_lock(stream);
+
+    *frames = stream->held_frames < stream->period_frames ? 0 : stream->period_frames;
+
+    return oss_unlock_result(stream, &params->result, S_OK);
+}
+
 static NTSTATUS set_event_handle(void *args)
 {
     struct set_event_handle_params *params = args;
@@ -1282,5 +1295,6 @@ unixlib_entry_t __wine_unix_call_funcs[] =
     get_buffer_size,
     get_latency,
     get_current_padding,
+    get_next_packet_size,
     set_event_handle,
 };
diff --git a/dlls/wineoss.drv/unixlib.h b/dlls/wineoss.drv/unixlib.h
index 2f0884b9ac5..a809ad41d3e 100644
--- a/dlls/wineoss.drv/unixlib.h
+++ b/dlls/wineoss.drv/unixlib.h
@@ -186,6 +186,13 @@ struct get_current_padding_params
     UINT32 *padding;
 };
 
+struct get_next_packet_size_params
+{
+    struct oss_stream *stream;
+    HRESULT result;
+    UINT32 *frames;
+};
+
 struct set_event_handle_params
 {
     struct oss_stream *stream;
@@ -212,6 +219,7 @@ enum oss_funcs
     oss_get_buffer_size,
     oss_get_latency,
     oss_get_current_padding,
+    oss_get_next_packet_size,
     oss_set_event_handle,
 };