diff --git a/validation-model/src/main/java/org/verapdf/gf/model/impl/pd/GFPDExtGState.java b/validation-model/src/main/java/org/verapdf/gf/model/impl/pd/GFPDExtGState.java
index 26fa2f95e..ac2ee61d7 100644
--- a/validation-model/src/main/java/org/verapdf/gf/model/impl/pd/GFPDExtGState.java
+++ b/validation-model/src/main/java/org/verapdf/gf/model/impl/pd/GFPDExtGState.java
@@ -145,6 +145,11 @@ public Boolean getcontainsSMask() {
         return simplePDObject.knownKey(ASAtom.SMASK);
     }
 
+    @Override
+    public Boolean getcontainsBM() {
+        return simplePDObject.knownKey(ASAtom.BM);
+    }
+
     @Override
     public String getBMNameValue() {
         return simplePDObject.getNameKeyStringValue(ASAtom.BM);