diff --git a/test/core/iomgr/combiner_test.c b/test/core/iomgr/combiner_test.c
index 92935ca01703e3dfd9117f6d58b06ec5f0833580..beb5c47623ef5b7e3832c8be124ea637a4351b6f 100644
--- a/test/core/iomgr/combiner_test.c
+++ b/test/core/iomgr/combiner_test.c
@@ -48,23 +48,25 @@ static void test_no_op(void) {
   grpc_exec_ctx_finish(&exec_ctx);
 }
 
-static void set_bool_to_true(grpc_exec_ctx *exec_ctx, void *value,
-                             grpc_error *error) {
-  *(bool *)value = true;
+static void set_event_to_true(grpc_exec_ctx *exec_ctx, void *value,
+                              grpc_error *error) {
+  gpr_event_set(value, (void *)1);
 }
 
 static void test_execute_one(void) {
   gpr_log(GPR_DEBUG, "test_execute_one");
 
   grpc_combiner *lock = grpc_combiner_create();
-  bool done = false;
+  gpr_event done;
+  gpr_event_init(&done);
   grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
   grpc_closure_sched(&exec_ctx,
-                     grpc_closure_create(set_bool_to_true, &done,
+                     grpc_closure_create(set_event_to_true, &done,
                                          grpc_combiner_scheduler(lock)),
                      GRPC_ERROR_NONE);
   grpc_exec_ctx_flush(&exec_ctx);
-  GPR_ASSERT(done);
+  GPR_ASSERT(gpr_event_wait(&done, grpc_timeout_seconds_to_deadline(5)) !=
+             NULL);
   GRPC_COMBINER_UNREF(&exec_ctx, lock, "test_execute_one");
   grpc_exec_ctx_finish(&exec_ctx);
 }
@@ -72,6 +74,7 @@ static void test_execute_one(void) {
 typedef struct {
   size_t ctr;
   grpc_combiner *lock;
+  gpr_event done;
 } thd_args;
 
 typedef struct {
@@ -105,6 +108,10 @@ static void execute_many_loop(void *a) {
     // picking it up
     gpr_sleep_until(grpc_timeout_milliseconds_to_deadline(100));
   }
+  grpc_closure_sched(&exec_ctx,
+                     grpc_closure_create(set_event_to_true, &args->done,
+                                         grpc_combiner_scheduler(args->lock)),
+                     GRPC_ERROR_NONE);
   grpc_exec_ctx_finish(&exec_ctx);
 }
 
@@ -119,9 +126,12 @@ static void test_execute_many(void) {
     gpr_thd_options_set_joinable(&options);
     ta[i].ctr = 0;
     ta[i].lock = lock;
+    gpr_event_init(&ta[i].done);
     GPR_ASSERT(gpr_thd_new(&thds[i], execute_many_loop, &ta[i], &options));
   }
   for (size_t i = 0; i < GPR_ARRAY_SIZE(thds); i++) {
+    GPR_ASSERT(gpr_event_wait(&ta[i].done,
+                              gpr_inf_future(GPR_CLOCK_REALTIME)) != NULL);
     gpr_thd_join(thds[i]);
   }
   grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
@@ -129,15 +139,15 @@ static void test_execute_many(void) {
   grpc_exec_ctx_finish(&exec_ctx);
 }
 
-static bool got_in_finally = false;
+static gpr_event got_in_finally;
 
 static void in_finally(grpc_exec_ctx *exec_ctx, void *arg, grpc_error *error) {
-  got_in_finally = true;
+  gpr_event_set(&got_in_finally, (void *)1);
 }
 
 static void add_finally(grpc_exec_ctx *exec_ctx, void *arg, grpc_error *error) {
   grpc_closure_sched(exec_ctx,
-                     grpc_closure_create(in_finally, NULL,
+                     grpc_closure_create(in_finally, arg,
                                          grpc_combiner_finally_scheduler(arg)),
                      GRPC_ERROR_NONE);
 }
@@ -147,12 +157,14 @@ static void test_execute_finally(void) {
 
   grpc_combiner *lock = grpc_combiner_create();
   grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
+  gpr_event_init(&got_in_finally);
   grpc_closure_sched(
       &exec_ctx,
       grpc_closure_create(add_finally, lock, grpc_combiner_scheduler(lock)),
       GRPC_ERROR_NONE);
   grpc_exec_ctx_flush(&exec_ctx);
-  GPR_ASSERT(got_in_finally);
+  GPR_ASSERT(gpr_event_wait(&got_in_finally,
+                            grpc_timeout_seconds_to_deadline(5)) != NULL);
   GRPC_COMBINER_UNREF(&exec_ctx, lock, "test_execute_finally");
   grpc_exec_ctx_finish(&exec_ctx);
 }