Careful upgrading to the latest OpenJDK release if you’re using OkHttp 3. The methods that the JDK 9 platform detection used now exist in 8 and cause runtime failures Actually, it looks like OkHttp 3.x works fine, it’s our Java 8 SslSocket wrapper that was causing the call to fall through and break. OkHttp 4 will need work to support ALPN on OpenJDK 8u252 and later though