diff --git a/ppapi/proxy/plugin_var_tracker.cc b/ppapi/proxy/plugin_var_tracker.cc
index c3a4c369f0d76..b8fcd568581d5 100644
--- a/ppapi/proxy/plugin_var_tracker.cc
+++ b/ppapi/proxy/plugin_var_tracker.cc
@@ -6,6 +6,8 @@
 
 #include <stddef.h>
 
+#include <limits>
+
 #include "base/memory/ref_counted.h"
 #include "base/memory/singleton.h"
 #include "ipc/ipc_message.h"
@@ -79,6 +81,7 @@ PP_Var PluginVarTracker::ReceiveObjectPassRef(const PP_Var& host_var,
     SendReleaseObjectMsg(*object.get());
   }
   info.ref_count++;
+  CHECK(info.ref_count != std::numeric_limits<decltype(info.ref_count)>::max());
   return ret;
 }
 
diff --git a/ppapi/shared_impl/var_tracker.cc b/ppapi/shared_impl/var_tracker.cc
index 0d777590bb5fd..40156b4895f05 100644
--- a/ppapi/shared_impl/var_tracker.cc
+++ b/ppapi/shared_impl/var_tracker.cc
@@ -83,6 +83,7 @@ bool VarTracker::AddRefVar(int32_t var_id) {
 
   // Basic refcount increment.
   info.ref_count++;
+  CHECK(info.ref_count != std::numeric_limits<decltype(info.ref_count)>::max());
   return true;
 }