diff --git a/ClosedXML/Utils/OpenXmlHelper.cs b/ClosedXML/Utils/OpenXmlHelper.cs
index 950ed19..3e1af4a 100644
--- a/ClosedXML/Utils/OpenXmlHelper.cs
+++ b/ClosedXML/Utils/OpenXmlHelper.cs
@@ -11,7 +11,7 @@
 
         public static bool GetBooleanValueAsBool(BooleanValue value, bool defaultValue)
         {
-            return value.HasValue ? value.Value : defaultValue;
+            return (value?.HasValue ?? false) ? value.Value : defaultValue;
         }
     }
 }