diff --git a/FreeBSD.md b/FreeBSD.md
index 39e4311..615f36b 100644
--- a/FreeBSD.md
+++ b/FreeBSD.md
@@ -2,6 +2,16 @@
 
 Ebiten requires X Window system and you need to install a window manager like gnome3. See [the official manual](https://www.freebsd.org/doc/handbook/x11-wm.html). Note that you also need to do `pkg install xorg`.
 
+# Set up environment variables
+
+On FreeBSD, `/usr/local/*` is not used by compilers by default. Set up some environment variables.
+
+```
+export C_INCLUDE_PATH=/usr/local/include:${C_INCLUDE_PATH}
+export CPLUS_INCLUDE_PATH=/usr/local/include:${CPLUS_INCLUDE_PATH}
+export LIBRARY_PATH=/usr/local/lib:${LIBRARY_PATH}
+```
+
 # Install dependencies
 
 Install Go via `pkg` command or [the official site](https://golang.org/).