diff --git a/validation-model/src/main/java/org/verapdf/gf/model/impl/pd/GFPDStructTreeNode.java b/validation-model/src/main/java/org/verapdf/gf/model/impl/pd/GFPDStructTreeNode.java
index 43b88edea..3033aa2f7 100644
--- a/validation-model/src/main/java/org/verapdf/gf/model/impl/pd/GFPDStructTreeNode.java
+++ b/validation-model/src/main/java/org/verapdf/gf/model/impl/pd/GFPDStructTreeNode.java
@@ -113,7 +113,7 @@ private static List<String> getChildrenStandardTypes(GFPDStructTreeNode element)
 
 	public List<GFPDStructElem> getChildren() {
 		if (children == null) {
-			List<org.verapdf.pd.structure.PDStructElem> elements = ((org.verapdf.pd.structure.PDStructElem) simplePDObject).getStructChildren();
+			List<org.verapdf.pd.structure.PDStructElem> elements = ((org.verapdf.pd.structure.PDStructTreeNode) simplePDObject).getStructChildren();
 			if (!elements.isEmpty()) {
 				List<GFPDStructElem> res = new ArrayList<>(elements.size());
 				for (org.verapdf.pd.structure.PDStructElem element : elements) {