diff --git a/hugolib/hugo_modules_test.go b/hugolib/hugo_modules_test.go
index 3353f508e..88a0c3ec6 100644
--- a/hugolib/hugo_modules_test.go
+++ b/hugolib/hugo_modules_test.go
@@ -1178,3 +1178,32 @@ target = "content/resources-b"
 	b.AssertFileContent("public/resources-a/subdir/about/index.html", "Single")
 	b.AssertFileContent("public/resources-b/subdir/about/index.html", "Single")
 }
+
+func TestMountData(t *testing.T) {
+	files := `
+-- hugo.toml --
+baseURL = 'https://example.org/'
+disableKinds = ["taxonomy", "term", "RSS", "sitemap", "robotsTXT", "page", "section"]
+
+[[module.mounts]]
+source = "data"
+target = "data"
+
+[[module.mounts]]
+source = "extra-data"
+target = "data/extra"
+-- extra-data/test.yaml --
+message: Hugo Rocks
+-- layouts/index.html --
+{{ site.Data.extra.test.message }}
+`
+
+	b := NewIntegrationTestBuilder(
+		IntegrationTestConfig{
+			T:           t,
+			TxtarString: files,
+		},
+	).Build()
+
+	b.AssertFileContent("public/index.html", "Hugo Rocks")
+}
diff --git a/hugolib/hugo_sites.go b/hugolib/hugo_sites.go
index de19a3669..3b5efa2e5 100644
--- a/hugolib/hugo_sites.go
+++ b/hugolib/hugo_sites.go
@@ -555,13 +555,14 @@ func (h *HugoSites) loadData(fis []hugofs.FileMetaInfo) (err error) {
 
 	h.data = make(map[string]any)
 	for _, fi := range fis {
+		basePath := fi.Meta().Path
 		fileSystem := spec.NewFilesystemFromFileMetaInfo(fi)
 		files, err := fileSystem.Files()
 		if err != nil {
 			return err
 		}
 		for _, r := range files {
-			if err := h.handleDataFile(r); err != nil {
+			if err := h.handleDataFile(basePath, r); err != nil {
 				return err
 			}
 		}
@@ -570,7 +571,7 @@ func (h *HugoSites) loadData(fis []hugofs.FileMetaInfo) (err error) {
 	return
 }
 
-func (h *HugoSites) handleDataFile(r source.File) error {
+func (h *HugoSites) handleDataFile(basePath string, r source.File) error {
 	var current map[string]any
 
 	f, err := r.FileInfo().Meta().Open()
@@ -581,7 +582,8 @@ func (h *HugoSites) handleDataFile(r source.File) error {
 
 	// Crawl in data tree to insert data
 	current = h.data
-	keyParts := strings.Split(r.Dir(), helpers.FilePathSeparator)
+	dataPath := filepath.Join(basePath, r.Dir())
+	keyParts := strings.Split(dataPath, helpers.FilePathSeparator)
 
 	for _, key := range keyParts {
 		if key != "" {