diff --git a/fpdfsdk/formfiller/cffl_checkbox.cpp b/fpdfsdk/formfiller/cffl_checkbox.cpp
index 03453a33e..c2588fd8d 100644
--- a/fpdfsdk/formfiller/cffl_checkbox.cpp
+++ b/fpdfsdk/formfiller/cffl_checkbox.cpp
@@ -51,15 +51,13 @@ bool CFFL_CheckBox::OnChar(CPDFSDK_Widget* pWidget,
       CPDFSDK_PageView* pPageView = pWidget->GetPageView();
       DCHECK(pPageView);
 
+      // If OnButtonUp() destroys |pObserved| (the owning CPDFSDK_Widget), its
+      // destructor has already destroyed |this| via
+      // CFFL_InteractiveFormFiller::OnDelete -> UnregisterFormField, so do not
+      // touch any members afterwards.
       ObservedPtr<CPDFSDK_Widget> pObserved(widget_);
-      if (form_filler_->OnButtonUp(pObserved, pPageView, nFlags)) {
-        if (!pObserved) {
-          widget_ = nullptr;
-        }
-        return true;
-      }
-      if (!pObserved) {
-        widget_ = nullptr;
+      if (form_filler_->OnButtonUp(pObserved, pPageView, nFlags) ||
+          !pObserved) {
         return true;
       }