diff --git a/internal/piwigo/piwigotools/tree.go b/internal/piwigo/piwigotools/tree.go
index 23cb82a..50e7127 100644
--- a/internal/piwigo/piwigotools/tree.go
+++ b/internal/piwigo/piwigotools/tree.go
@@ -3,17 +3,19 @@ package piwigotools
 import (
 	"path/filepath"
 	"sort"
+	"strings"
 )
 
 type Tree interface {
-	AddNode(string) Tree
+	Add(string) Tree
+	AddPath(string) Tree
 	FlatView() chan string
 	TreeView() chan string
 }
 
 type node struct {
 	Name     string
-	Children []*node
+	children map[string]*node
 }
 
 func NewTree() Tree {
@@ -22,11 +24,41 @@ func NewTree() Tree {
 	}
 }
 
-func (t *node) AddNode(name string) Tree {
-	n := &node{Name: name}
-	t.Children = append(t.Children, n)
+func (t *node) Add(name string) Tree {
+	if t.children == nil {
+		t.children = map[string]*node{}
+	}
+	n, ok := t.children[name]
+	if !ok {
+		n = &node{Name: name}
+		t.children[name] = n
+	}
 	return n
 }
+func (t *node) AddPath(path string) Tree {
+	n := Tree(t)
+	for _, name := range strings.Split(path, "/") {
+		n = n.Add(name)
+	}
+	return n
+}
+
+func (t *node) Children() []*node {
+	childs := make([]*node, len(t.children))
+	i := 0
+	for _, n := range t.children {
+		childs[i] = n
+		i++
+	}
+	sort.Slice(childs, func(i, j int) bool {
+		return childs[i].Name < childs[j].Name
+	})
+	return childs
+}
+
+func (t *node) HasChildren() bool {
+	return t.children != nil
+}
 
 func (t *node) FlatView() (out chan string) {
 	out = make(chan string)
@@ -35,14 +67,11 @@ func (t *node) FlatView() (out chan string) {
 		var flatten func(string, *node)
 
 		flatten = func(path string, t *node) {
-			switch t.Children {
-			case nil:
+			switch t.HasChildren() {
+			case false:
 				out <- path
-			default:
-				sort.Slice(t.Children, func(i, j int) bool {
-					return t.Children[i].Name < t.Children[j].Name
-				})
-				for _, child := range t.Children {
+			case true:
+				for _, child := range t.Children() {
 					flatten(filepath.Join(path, child.Name), child)
 				}
 			}
@@ -66,9 +95,10 @@ func (t *node) TreeView() (out chan string) {
 		var tree func(string, *node)
 
 		tree = func(prefix string, t *node) {
-			for i, st := range t.Children {
+			children := t.Children()
+			for i, st := range children {
 				switch i {
-				case len(t.Children) - 1:
+				case len(children) - 1:
 					out <- prefix + treeEndChar + st.Name
 					tree(prefix+treeAfterEndChar, st)
 				case 0:
@@ -83,7 +113,6 @@ func (t *node) TreeView() (out chan string) {
 
 		out <- t.Name
 		tree("", t)
-
 	}()
 	return out
 }
diff --git a/internal/piwigocli/images_list.go b/internal/piwigocli/images_list.go
index 2d5b69a..9b6fafa 100644
--- a/internal/piwigocli/images_list.go
+++ b/internal/piwigocli/images_list.go
@@ -60,7 +60,6 @@ func (c *ImagesListCommand) Execute(args []string) error {
 	}
 
 	rootTree := piwigotools.NewTree()
-	cache := map[string]piwigotools.Tree{}
 
 	bar := progressbar.Default(1, "listing")
 	for page := 0; ; page++ {
@@ -81,29 +80,14 @@ func (c *ImagesListCommand) Execute(args []string) error {
 
 		for _, image := range resp.Images {
 			for _, cat := range image.Categories {
-				categoryPath := strings.Split(categories[cat.Id].Name[len(rootCatName):], " / ")
-				if !filter.MatchString(
-					filepath.Join(
-						filepath.Join(categoryPath...),
-						image.Filename,
-					),
-				) {
+				filename := filepath.Join(
+					strings.ReplaceAll(categories[cat.Id].Name[len(rootCatName):], " / ", "/"),
+					image.Filename,
+				)
+				if !filter.MatchString(filename) {
 					continue
 				}
-				curpath := ""
-				cur := rootTree
-				for _, path := range categoryPath {
-					curpath = filepath.Join(curpath, path)
-					node, ok := cache[curpath]
-					switch ok {
-					case true:
-						cur = node
-					case false:
-						cur = cur.AddNode(path)
-						cache[curpath] = cur
-					}
-				}
-				cur.AddNode(image.Filename)
+				rootTree.AddPath(filename)
 			}
 			bar.Add(1)
 		}