Update THANKS.
diff --git a/THANKS b/THANKS
index f56e91c..ee86a14 100644
--- a/THANKS
+++ b/THANKS
@@ -91,6 +91,7 @@
   - Andreas Schwab
   - Dan Shechter
   - Stuart Shelton
+  - Sebastian Andrzej Siewior
   - Brad Smith
   - Jonathan Stott
   - Dan Stromberg