diff --git a/python/src/com/jetbrains/python/psi/impl/PyFileImpl.java b/python/src/com/jetbrains/python/psi/impl/PyFileImpl.java
index 294c92bbdcb4..0a543f1c255f 100644
--- a/python/src/com/jetbrains/python/psi/impl/PyFileImpl.java
+++ b/python/src/com/jetbrains/python/psi/impl/PyFileImpl.java
@@ -510,7 +510,7 @@ public class PyFileImpl extends PsiFileBase implements PyFile, PyExpression {
   }
 
   private static class DunderAllBuilder extends PyRecursiveElementVisitor {
-    private List<String> myResult = null;
+    private List<String> myResult = new ArrayList<>();
     private boolean myDynamic = false;
     private boolean myFoundDunderAll = false;