diff --git a/proguard.flags b/proguard.flags
new file mode 100644
index 0000000..160020b
--- /dev/null
+++ b/proguard.flags
@@ -0,0 +1,4 @@
+# These are referenced by com.google.common.util.concurrent and
+# com.google.errorprone.annotations but don't exist on Android.
+-dontwarn java.lang.ClassValue
+-dontwarn javax.lang.model.element.Modifier
\ No newline at end of file