Fix Proguard flags.
diff --git a/packages/TtsService/proguard.flags b/packages/TtsService/proguard.flags
new file mode 100644
index 0000000..e8bee6b
--- /dev/null
+++ b/packages/TtsService/proguard.flags
@@ -0,0 +1,5 @@
+-keep class android.tts.SynthProxy {
+  int mJniData;
+  # keep all declarations for native methods
+  <methods>;
+}