In Android app when minifyEnabled true my FAB doesn't animate up to make room for snackbar -

in android app (using android studio) i'm using com.android.support:design:22.2.0 floating action button, , snackbar.

when building app while minifyenabled false fab animates upwards , downwards appearance , dismissal of snackbar expected (as far know on every supported android version). however, when built minifyenabled true , ran on device api version of 21 or below fab not animated, rather covers or covered snackbar, depending on android version.

my proguard rules defaults, proguard-rules.pro populated comments.

 proguardfiles getdefaultproguardfile('proguard-android.txt'), 'proguard-rules.pro' 

any insight why might happening appreciated!

as inspired https://stackoverflow.com/a/28200571/863753 have fixed issue adding following proguard-rules.pro file:

    -keep class android.support.design.widget.** { *; }     -keep interface android.support.design.widget.** { *; }