diff --git a/mod.go b/mod.go
index a10023f..807444a 100644
--- a/mod.go
+++ b/mod.go
@@ -53,6 +53,11 @@ func PkgSourceDir(pkgPath, modDir string, replace bool) (dir string, err error)
 			continue
 		}
 		suffix := strings.TrimPrefix(pkgPath, pkg.Mod.Path)
+		// github.com/issue9/web 与 github.com/issue9/webuse 也匹配，但不是同一个包
+		// 只有 github.com/issue9/web 与 github.com/issue9/web/v4 这种才行
+		if suffix != "" && suffix[0] != '/' {
+			continue
+		}
 
 		if !replace {
 			return filepath.Join(pkgSource, pkg.Mod.Path+"@"+pkg.Mod.Version+suffix), nil
diff --git a/mod_test.go b/mod_test.go
index a2cc7eb..acdca16 100644
--- a/mod_test.go
+++ b/mod_test.go
@@ -34,6 +34,9 @@ func TestPkgSourceDir(t *testing.T) {
 	a.NotError(err).FileExists(dir).
 		True(strings.HasSuffix(filepath.ToSlash(dir), "assert/v4@v4.3.0/rest"))
 
+	dir, err = PkgSourceDir("github.com/issue9/assertxx", "./", false)
+	a.ErrorIs(err, fs.ErrNotExist)
+
 	// replace
 
 	dir, err = PkgSourceDir("github.com/issue9/web/v2", "./testdata/go.mod", true)