Proguard still fails with retrolambda 2.5.1 targeting Java 7

[Perseverance1139]

Proguard reports error for each lambda usage:
can't find referenced class java.lang.invoke.MethodHandles$Lookup
can't find referenced class java.lang.invoke.MethodHandles

It is an android application.

Looking at this line here, I wonder should we remove methodhandles for Java 7 as well?
https://github.com/orfjackal/retrolambda/blob/6d5a4c1fd9d094452cfde2096a81ab82a0c1c9ce/retrolambda/src/main/java/net/orfjackal/retrolambda/Transformers.java#L116

Thanks!

[luontola]

Methodhandles were added in Java 7 (https://docs.oracle.com/javase/7/docs/api/java/lang/invoke/MethodHandles.html), but maybe Android's "Java 7" is not really Java 7 compatible and is missing some APIs. Does it work if you instead target Java 6?