Note 9front may not have IPv6 address ::1 configured
diff --git a/Plan9.md b/Plan9.md
index 1886264..28d0d5d 100644
--- a/Plan9.md
+++ b/Plan9.md
@@ -45,6 +45,10 @@
CA certificates for `crypto/x509` package needs to be installed at `/sys/lib/tls/ca.pem`. You can download it from `https://curl.haxx.se/ca/cacert.pem` or copy from another system.
+For 9front, you may need to configure IPv6 loopback address for standard library tests:
+
+ ip/ipconfig -P loopback /dev/null ::1
+
# Installation
Since Go is written in Go, you may want to bootstrap Go with Go 1.4.3, which is the latest release of Go written in C.
