diff --git a/cmd/godoc/godoc_test.go b/cmd/godoc/godoc_test.go
index 483b8643..97b00d0c 100644
--- a/cmd/godoc/godoc_test.go
+++ b/cmd/godoc/godoc_test.go
@@ -44,9 +44,7 @@ var godocTests = []struct {
 	{
 		args: []string{"nonexistingpkg"},
 		matches: []string{
-			// The last pattern (does not e) is for plan9:
-			// http://build.golang.org/log/2d8e5e14ed365bfa434b37ec0338cd9e6f8dd9bf
-			`no such file or directory|does not exist|cannot find the file|(?:' does not e)`,
+			`cannot find package`,
 		},
 	},
 	{
diff --git a/godoc/server.go b/godoc/server.go
index 104e75b6..162e5a6a 100644
--- a/godoc/server.go
+++ b/godoc/server.go
@@ -65,6 +65,10 @@ func (h *handlerServer) GetPageInfo(abspath, relpath string, mode PageInfoMode,
 	// are used.
 	ctxt := build.Default
 	ctxt.IsAbsPath = pathpkg.IsAbs
+	ctxt.IsDir = func(path string) bool {
+		fi, err := h.c.fs.Stat(filepath.ToSlash(path))
+		return err == nil && fi.IsDir()
+	}
 	ctxt.ReadDir = func(dir string) ([]os.FileInfo, error) {
 		f, err := h.c.fs.ReadDir(filepath.ToSlash(dir))
 		filtered := make([]os.FileInfo, 0, len(f))