diff -r b16a53f58594 src/cmd/godoc/main.go
--- a/src/cmd/godoc/main.go	Thu Dec 22 14:21:25 2011 +1100
+++ b/src/cmd/godoc/main.go	Thu Dec 22 15:14:13 2011 +1100
@@ -368,6 +368,8 @@
 		return
 	}

+	initDirTrees()
+
 	// determine paths
 	path := flag.Arg(0)
 	if len(path) > 0 && path[0] == '.' {