diff --git a/fpdfsdk/pwl/cpwl_timer.cpp b/fpdfsdk/pwl/cpwl_timer.cpp
index 44fc32c..902a144 100644
--- a/fpdfsdk/pwl/cpwl_timer.cpp
+++ b/fpdfsdk/pwl/cpwl_timer.cpp
@@ -36,7 +36,8 @@
   KillPWLTimer();
 
   m_nTimerID = m_pSystemHandler->SetTimer(nElapse, TimerProc);
-  GetPWLTimeMap()[m_nTimerID] = this;
+  if (HasValidID())
+    GetPWLTimeMap()[m_nTimerID] = this;
   return m_nTimerID;
 }