diff --git a/validation-model/src/main/java/org/verapdf/gf/model/impl/pd/images/GFPDXForm.java b/validation-model/src/main/java/org/verapdf/gf/model/impl/pd/images/GFPDXForm.java
index bd0ef39f8..4b8fda652 100644
--- a/validation-model/src/main/java/org/verapdf/gf/model/impl/pd/images/GFPDXForm.java
+++ b/validation-model/src/main/java/org/verapdf/gf/model/impl/pd/images/GFPDXForm.java
@@ -115,7 +115,7 @@ private List<PDGroup> getGroup() {
 
 	public PDColorSpace getBlendingColorSpace() {
 		org.verapdf.pd.PDGroup group = ((org.verapdf.pd.images.PDXForm) this.simplePDObject).getGroup();
-		if (group == null || !ASAtom.TRANSPARENCY.equals(group.getSubtype())) {
+		if (group == null || !ASAtom.TRANSPARENCY.equals(group.getSubtype()) || !group.isIsolated()) {
 			return null;
 		}
 		PDColorSpace colorSpace = group.getColorSpace();