diff --git a/nexgb/Makefile b/nexgb/Makefile
index 7a3dae2..c0ee531 100644
--- a/nexgb/Makefile
+++ b/nexgb/Makefile
@@ -10,7 +10,9 @@
 # Go package.
 
 # My path to the X protocol XML descriptions.
+ifndef XPROTO
 XPROTO=/usr/share/xcb
+endif
 
 # All of the XML files in my /usr/share/xcb directory EXCEPT XKB. -_-
 # This is intended to build xgbgen and generate Go code for each supported