diff --git a/collective/limitfilesizepanel/dx_validators.py b/collective/limitfilesizepanel/dx_validators.py
index 6894382..ce41f20 100644
--- a/collective/limitfilesizepanel/dx_validators.py
+++ b/collective/limitfilesizepanel/dx_validators.py
@@ -41,7 +41,7 @@ def helper_view(self):
                 request=self.request,
             )
         except InvalidParameterError:
-            return True
+            return None
 
     def __call__(self):
         if not self.value:
diff --git a/docs/HISTORY.rst b/docs/HISTORY.rst
index 6248586..86182e0 100644
--- a/docs/HISTORY.rst
+++ b/docs/HISTORY.rst
@@ -4,7 +4,8 @@ Changelog
 3.0.3 (unreleased)
 ------------------
 
-- Nothing changed yet.
+- Fix check in validators if product is not installed.
+  [cekk]
 
 
 3.0.2 (2023-05-02)