diff --git a/src/decoder/plugins/SndfileDecoderPlugin.cxx b/src/decoder/plugins/SndfileDecoderPlugin.cxx
index 94c2e964e..953c15c62 100644
--- a/src/decoder/plugins/SndfileDecoderPlugin.cxx
+++ b/src/decoder/plugins/SndfileDecoderPlugin.cxx
@@ -212,7 +212,7 @@ sndfile_stream_decode(DecoderClient &client, InputStream &is)
 			break;
 
 		cmd = client.SubmitAudio(is,
-					 std::span{buffer, num_frames * frame_size},
+					 std::span{buffer, static_cast<size_t>(num_frames) * frame_size},
 					 0);
 		if (cmd == DecoderCommand::SEEK) {
 			sf_count_t c = client.GetSeekFrame();