src/cmd/go/pkg.go | 2 +-

diff --git a/src/cmd/go/pkg.go b/src/cmd/go/pkg.go
index 51567b5afbef9b55638cd9a142586f339bb4c6ad..f949d4e9f22e743aed49ac3bc44714f6324381e4 100644
--- a/src/cmd/go/pkg.go
+++ b/src/cmd/go/pkg.go
@@ -355,7 +355,7 @@ // If no epxansion is found, vendoredImportPath also returns a list of vendor directories
 // it searched along the way, to help prepare a useful error message should path turn
 // out not to exist.
 func vendoredImportPath(parent *Package, path string) (found string, searched []string) {
-	if parent == nil || !go15VendorExperiment {
+	if parent == nil || parent.Root == "" || !go15VendorExperiment {
 		return path, nil
 	}
 	dir := filepath.Clean(parent.Dir)