diff --git a/src/org/geometerplus/fbreader/library/AuthorTree.java b/src/org/geometerplus/fbreader/library/AuthorTree.java
index 7ac7419f6..1188b5a99 100644
--- a/src/org/geometerplus/fbreader/library/AuthorTree.java
+++ b/src/org/geometerplus/fbreader/library/AuthorTree.java
@@ -43,7 +43,7 @@ public class AuthorTree extends LibraryTree {
 
 	@Override
 	protected String getStringId() {
-		return getName() + ":" + getSortKey();
+		return "@AuthorTree" + getName() + ":" + getSortKey();
 	}
 
 	@Override
diff --git a/src/org/geometerplus/fbreader/library/BookTree.java b/src/org/geometerplus/fbreader/library/BookTree.java
index 853bf450e..3459e6cb5 100644
--- a/src/org/geometerplus/fbreader/library/BookTree.java
+++ b/src/org/geometerplus/fbreader/library/BookTree.java
@@ -54,7 +54,7 @@ public class BookTree extends LibraryTree {
 
 	@Override
 	protected String getStringId() {
-		return getName();
+		return "@BookTree " + getName();
 	}
 
 	@Override
diff --git a/src/org/geometerplus/fbreader/library/SeriesTree.java b/src/org/geometerplus/fbreader/library/SeriesTree.java
index 150ac9f78..8ff0915a2 100644
--- a/src/org/geometerplus/fbreader/library/SeriesTree.java
+++ b/src/org/geometerplus/fbreader/library/SeriesTree.java
@@ -40,7 +40,7 @@ public final class SeriesTree extends LibraryTree {
 
 	@Override
 	protected String getStringId() {
-		return getName();
+		return "@SeriesTree " + getName();
 	}
 
 	BookTree getBookInSeriesSubTree(Book book) {
diff --git a/src/org/geometerplus/fbreader/library/TagTree.java b/src/org/geometerplus/fbreader/library/TagTree.java
index 336b07d5f..51f5313b5 100644
--- a/src/org/geometerplus/fbreader/library/TagTree.java
+++ b/src/org/geometerplus/fbreader/library/TagTree.java
@@ -39,7 +39,7 @@ public final class TagTree extends LibraryTree {
 
 	@Override
 	protected String getStringId() {
-		return getName();
+		return "@TagTree " + getName();
 	}
 
 	protected String getSortKey() {
diff --git a/src/org/geometerplus/fbreader/library/TitleTree.java b/src/org/geometerplus/fbreader/library/TitleTree.java
index 2bedefcbc..f4565efd3 100644
--- a/src/org/geometerplus/fbreader/library/TitleTree.java
+++ b/src/org/geometerplus/fbreader/library/TitleTree.java
@@ -59,7 +59,7 @@ public final class TitleTree extends LibraryTree {
 
 	@Override
 	protected String getStringId() {
-		return getName();
+		return "@TitleTree " + getName();
 	}
 
 	@Override