diff --git a/test/cctest/heap/test-heap.cc b/test/cctest/heap/test-heap.cc
index ccc397e949..052f031b4e 100644
--- a/test/cctest/heap/test-heap.cc
+++ b/test/cctest/heap/test-heap.cc
@@ -1281,6 +1281,7 @@ TEST(TestOptimizeAfterBytecodeFlushingCandidate) {
   i::FLAG_incremental_marking = true;
   i::FLAG_flush_bytecode = true;
   i::FLAG_allow_natives_syntax = true;
+  ManualGCScope manual_gc_scope;
 
   CcTest::InitializeVM();
   Isolate* isolate = CcTest::i_isolate();
diff --git a/test/cctest/test-heap-profiler.cc b/test/cctest/test-heap-profiler.cc
index 27c4e54f02..2a6ef85d6b 100644
--- a/test/cctest/test-heap-profiler.cc
+++ b/test/cctest/test-heap-profiler.cc
@@ -1263,6 +1263,9 @@ static TestStatsStream GetHeapStatsUpdate(
 
 
 TEST(HeapSnapshotObjectsStats) {
+  // Concurrent allocation might break results
+  v8::internal::FLAG_stress_concurrent_allocation = false;
+
   LocalContext env;
   v8::HandleScope scope(env->GetIsolate());
   v8::HeapProfiler* heap_profiler = env->GetIsolate()->GetHeapProfiler();