diff --git a/pdfbox-validation-model/src/main/java/org/verapdf/model/impl/pb/pd/PBoxPDExtGState.java b/pdfbox-validation-model/src/main/java/org/verapdf/model/impl/pb/pd/PBoxPDExtGState.java
index 4e05242a..e9f1b61d 100644
--- a/pdfbox-validation-model/src/main/java/org/verapdf/model/impl/pb/pd/PBoxPDExtGState.java
+++ b/pdfbox-validation-model/src/main/java/org/verapdf/model/impl/pb/pd/PBoxPDExtGState.java
@@ -109,6 +109,11 @@ public Boolean getcontainsSMask() {
 		return ((COSDictionary)simplePDObject.getCOSObject()).containsKey(COSName.SMASK);
 	}
 
+	@Override
+	public Boolean getcontainsBM() {
+		return ((COSDictionary)simplePDObject.getCOSObject()).containsKey(COSName.BM);
+	}
+
 	@Override
 	public String getBMNameValue() {
 		return getNameKeyStringValue((COSDictionary)simplePDObject.getCOSObject(), COSName.BM);