diff --git a/src/core/lib/iomgr/timer_custom.cc b/src/core/lib/iomgr/timer_custom.cc
index 71d825ff9f5..57675c27a8f 100644
--- a/src/core/lib/iomgr/timer_custom.cc
+++ b/src/core/lib/iomgr/timer_custom.cc
@@ -32,6 +32,7 @@ static grpc_custom_timer_vtable* custom_timer_impl;
 
 void grpc_custom_timer_callback(grpc_custom_timer* t, grpc_error* error) {
   GRPC_CUSTOM_IOMGR_ASSERT_SAME_THREAD();
+  grpc_core::ApplicationCallbackExecCtx callback_exec_ctx;
   grpc_core::ExecCtx exec_ctx;
   grpc_timer* timer = t->original;
   GPR_ASSERT(timer->pending);