diff --git a/go/loader/stdlib_test.go b/go/loader/stdlib_test.go
index 1fdecef8..e8d93637 100644
--- a/go/loader/stdlib_test.go
+++ b/go/loader/stdlib_test.go
@@ -35,7 +35,7 @@ func allPackages() []string {
 			return filepath.SkipDir
 		}
 		if info.IsDir() {
-			pkg := strings.TrimPrefix(path, root)
+			pkg := filepath.ToSlash(strings.TrimPrefix(path, root))
 			switch pkg {
 			case "builtin", "pkg":
 				return filepath.SkipDir // skip these subtrees