Fix broken build

Change-Id: I51af52c9ddcae1675d15eb37a2f48fd0b3cd09c3
diff --git a/proguard.flags b/proguard.flags
index 72b6e65..ad6f727 100644
--- a/proguard.flags
+++ b/proguard.flags
@@ -86,7 +86,7 @@
 # next row when focus is on the last item of last row when using a RecyclerView
 # Keep optimized and shrunk proguard to prevent issues like this when using
 # support jar.
--keep allowoptimization,allowshrinking class android.support.** {
+-keep,allowoptimization,allowshrinking class android.support.** {
   *;
 }