diff --git a/csharp/ql/lib/semmle/code/csharp/dataflow/Nullness.qll b/csharp/ql/lib/semmle/code/csharp/dataflow/Nullness.qll
index 756fd6a4e3a..c7ac34d3d01 100644
--- a/csharp/ql/lib/semmle/code/csharp/dataflow/Nullness.qll
+++ b/csharp/ql/lib/semmle/code/csharp/dataflow/Nullness.qll
@@ -47,7 +47,8 @@ private Expr maybeNullExpr(Expr reason) {
   result =
     any(QualifiableExpr qe |
       qe.isConditional() and
-      qe.getQualifier() = maybeNullExpr(reason)
+      reason = qe.getQualifier() and
+      not qe instanceof AssignableWrite
     )
 }