diff --git a/libgo/README.gcc b/libgo/README.gcc
index d8bda190c9e..d5aabb0f9c2 100644
--- a/libgo/README.gcc
+++ b/libgo/README.gcc
@@ -1,3 +1,7 @@
 The files in this directory are mirrored from the gofrontend project
 hosted at http://code.google.com/p/gofrontend.  These files are the
 ones in the libgo subdirectory of that project.
+
+By default, the networking tests are not run.  In order to run all the
+libgo tests, you need to define the environment variable
+GCCGO_RUN_ALL_TESTS to a non-empty string.