diff --git a/src/core/catalog.js b/src/core/catalog.js
index 30fead7ad..b12abee83 100644
--- a/src/core/catalog.js
+++ b/src/core/catalog.js
@@ -354,15 +354,11 @@ class Catalog {
   }
 
   #readStructTreeRoot() {
-    const rawObj = this.#catDict.getRaw("StructTreeRoot");
-    const obj = this.xref.fetchIfRef(rawObj);
-    if (!(obj instanceof Dict)) {
-      return null;
-    }
-
-    const root = new StructTreeRoot(this.xref, obj, rawObj);
-    root.init();
-    return root;
+    const rawObj = this.#catDict.getRaw("StructTreeRoot"),
+      obj = this.xref.fetchIfRef(rawObj);
+    return obj instanceof Dict
+      ? new StructTreeRoot(this.xref, obj, rawObj)
+      : null;
   }
 
   get toplevelPagesDict() {
diff --git a/src/core/struct_tree.js b/src/core/struct_tree.js
index 8bfa3f186..722927a8b 100644
--- a/src/core/struct_tree.js
+++ b/src/core/struct_tree.js
@@ -37,14 +37,31 @@ const StructElementType = {
 };
 
 class StructTreeRoot {
+  kidRefToPosition = undefined;
+
+  parentTree = null;
+
+  roleMap = new Map();
+
+  structParentIds = null;
+
   constructor(xref, rootDict, rootRef) {
     this.xref = xref;
     this.dict = rootDict;
     this.ref = rootRef instanceof Ref ? rootRef : null;
-    this.roleMap = new Map();
-    this.structParentIds = null;
-    this.kidRefToPosition = undefined;
-    this.parentTree = null;
+
+    const roleMap = rootDict.get("RoleMap");
+    if (roleMap instanceof Dict) {
+      for (const [key, value] of roleMap) {
+        if (value instanceof Name) {
+          this.roleMap.set(key, value.name);
+        }
+      }
+    }
+    const parentTree = rootDict.getRaw("ParentTree");
+    if (parentTree) {
+      this.parentTree = new NumberTree(parentTree, xref);
+    }
   }
 
   getKidPosition(kidRef) {
@@ -71,15 +88,6 @@ class StructTreeRoot {
       : -1;
   }
 
-  init() {
-    this.readRoleMap();
-    const parentTree = this.dict.get("ParentTree");
-    if (!parentTree) {
-      return;
-    }
-    this.parentTree = new NumberTree(parentTree, this.xref);
-  }
-
   #addIdToPage(pageRef, id, type) {
     if (!(pageRef instanceof Ref) || id < 0) {
       return;
@@ -97,18 +105,6 @@ class StructTreeRoot {
     this.#addIdToPage(pageRef, id, StructElementType.ANNOTATION);
   }
 
-  readRoleMap() {
-    const roleMapDict = this.dict.get("RoleMap");
-    if (!(roleMapDict instanceof Dict)) {
-      return;
-    }
-    for (const [key, value] of roleMapDict) {
-      if (value instanceof Name) {
-        this.roleMap.set(key, value.name);
-      }
-    }
-  }
-
   static async canCreateStructureTree({
     catalogRef,
     pdfManager,