diff --git a/README.md b/README.md
index cd453809e4..29bb66bfd0 100644
--- a/README.md
+++ b/README.md
@@ -154,6 +154,7 @@ make`) or at the top of each application's Makefile.
     level](http://legion.stanford.edu/debugging/#logging-infrastructure).
   * `USE_CUDA=<0,1>`: enables CUDA support.
   * `USE_GASNET=<0,1>`: enables GASNet support (see [installation instructions](http://legion.stanford.edu/gasnet/)).
+  * `REALM_NETWORKS=<gasnet1,mpi>`: enables the GASNet or MPI backend for Realm.
   * `USE_LLVM=<0,1>`: enables LLVM support.
   * `USE_HDF=<0,1>`: enables HDF5 support.