diff --git a/src/hotspot/share/gc/serial/serialHeap.cpp b/src/hotspot/share/gc/serial/serialHeap.cpp
index 03ad1282f5f63..faef3b8912588 100644
--- a/src/hotspot/share/gc/serial/serialHeap.cpp
+++ b/src/hotspot/share/gc/serial/serialHeap.cpp
@@ -304,9 +304,12 @@ HeapWord* SerialHeap::mem_allocate_work(size_t size, bool is_tlab) {
   HeapWord* result = nullptr;
 
   for (uint try_count = 1; /* break */; try_count++) {
-    result = mem_allocate_cas_noexpand(size, is_tlab);
-    if (result != nullptr) {
-      break;
+    {
+      ConditionalMutexLocker locker(Heap_lock, !is_init_completed());
+      result = mem_allocate_cas_noexpand(size, is_tlab);
+      if (result != nullptr) {
+        break;
+      }
     }
     uint gc_count_before;  // Read inside the Heap_lock locked region.
     {
@@ -320,10 +323,15 @@ HeapWord* SerialHeap::mem_allocate_work(size_t size, bool is_tlab) {
       }
 
       if (!is_init_completed()) {
-        // Can't do GC; try heap expansion to satisfy the request.
-        result = expand_heap_and_allocate(size, is_tlab);
-        if (result != nullptr) {
-          return result;
+        // Double checked locking, this ensure that is_init_completed() does not
+        // transition while expanding the heap.
+        MonitorLocker ml(InitCompleted_lock, Monitor::_no_safepoint_check_flag);
+        if (!is_init_completed()) {
+          // Can't do GC; try heap expansion to satisfy the request.
+          result = expand_heap_and_allocate(size, is_tlab);
+          if (result != nullptr) {
+            return result;
+          }
         }
       }