Android : Proguard google play services jar

I'm trying to obfuscate google play services jar with proguard. I tried two versions of the proguard config file.

1. 
   

   First one contains

   
   

   
   -keep class ** {
       public protected *;
   }
   
   

And the jar stays not obfuscated. It looks ok.

2. 
   

   Second one contains

   
   

   
   -keep class com.** {
       public protected *;
   }
   
   

And proguard deletes everithing. I get an error:

    Error: The output jar is empty. Did you specify the proper '-keep' options?

Why is it empty, as the main google play services package is com.google.android.gms?