diff --git a/internal/collect.go b/internal/collect.go
index de9566d..0a6f994 100644
--- a/internal/collect.go
+++ b/internal/collect.go
@@ -20,6 +20,17 @@ type testf struct {
 	Name string
 }
 
+func isGoModule(path string) bool {
+	_, err := os.Lstat(filepath.Join(path, "go.mod"))
+	if os.IsNotExist(err) {
+		return false
+	}
+	if err != nil {
+		panic(err)
+	}
+	return true
+}
+
 func Collect(root string) ([]testf, error) {
 	tests := []testf{}
 	err := filepath.Walk(root, func(path string, info os.FileInfo, err error) error {
@@ -28,7 +39,9 @@ func Collect(root string) ([]testf, error) {
 		}
 
 		// Don't collect testdata directories.
-		if info.IsDir() && filepath.Base(info.Name()) == "testdata" {
+		if info.IsDir() &&
+			(filepath.Base(info.Name()) == "testdata" || filepath.Base(info.Name()) == "vendor" ||
+				(info.Name() != root && isGoModule(info.Name()))) {
 			return filepath.SkipDir
 		}
 
diff --git a/main.go b/main.go
index 1d8d1ab..c3fb927 100644
--- a/main.go
+++ b/main.go
@@ -73,8 +73,8 @@ func (p prog) run() (string, error) {
 
 	switch p.output {
 	case "env":
-		return fmt.Sprintf("SHARD_TESTS=%s\nSHARD_PATHS=%s", pattern, strings.Join(paths, " ")), nil
+		return fmt.Sprintf(`SHARD_TESTS="%s"\nSHARD_PATHS="%s"`, pattern, strings.Join(paths, " ")), nil
 	default:
-		return fmt.Sprintf("-run %s  %s", pattern, strings.Join(paths, " ")), nil
+		return fmt.Sprintf(`-run "%s"  %s`, pattern, strings.Join(paths, " ")), nil
 	}
 }