Updated Worker (markdown)

Worker.md

@@ -33,11 +33,12 @@ Installing this package will only speed up build process, otherwise libarchive i
 
 **Install Isolate from source**
 
-First, we need to compile sandbox Isolate from source and install. Assume that we keep source code in `/opt/src` dir. For building man page you need to have package `asciidoc` installed.
+First, we need to compile sandbox Isolate from source and install it. Current worker is tested against version 1.3, so this version needs to be checked out. Assume that we keep source code in `/opt/src` dir. For building man page you need to have package `asciidoc` installed.
 ```
 $ cd /opt/src
 $ git clone https://github.com/ioi/isolate.git
 $ cd isolate
+$ git checkout v1.3
 $ make
 # make install && make install-doc
 ```