diff --git a/1.4/source/RJW_Menstruation/RJW_Menstruation/Hediff_MultiplePregnancy.cs b/1.4/source/RJW_Menstruation/RJW_Menstruation/Hediff_MultiplePregnancy.cs
index 119613e..ae68491 100644
--- a/1.4/source/RJW_Menstruation/RJW_Menstruation/Hediff_MultiplePregnancy.cs
+++ b/1.4/source/RJW_Menstruation/RJW_Menstruation/Hediff_MultiplePregnancy.cs
@@ -634,8 +634,8 @@ namespace RJW_Menstruation
             }
             XenotypeDef motherInheritableXenotype = mother?.genes?.Xenotype;
             XenotypeDef fatherInheritableXenotype = father?.genes?.Xenotype;
-            if (!motherInheritableXenotype.inheritable) motherInheritableXenotype = null;
-            if (!fatherInheritableXenotype.inheritable) fatherInheritableXenotype = null;
+            if (!(motherInheritableXenotype?.inheritable ?? false)) motherInheritableXenotype = null;
+            if (!(fatherInheritableXenotype?.inheritable ?? false)) fatherInheritableXenotype = null;
 
             // If they're the same (or both null)
             if (motherInheritableXenotype == fatherInheritableXenotype)