diff --git a/src/heap/memory-allocator.h b/src/heap/memory-allocator.h
index 72f7943e1d..74d9b6bca5 100644
--- a/src/heap/memory-allocator.h
+++ b/src/heap/memory-allocator.h
@@ -330,12 +330,14 @@ class MemoryAllocator {
   }
 
   void RegisterExecutableMemoryChunk(MemoryChunk* chunk) {
+    base::MutexGuard guard(&executable_memory_mutex_);
     DCHECK(chunk->IsFlagSet(MemoryChunk::IS_EXECUTABLE));
     DCHECK_EQ(executable_memory_.find(chunk), executable_memory_.end());
     executable_memory_.insert(chunk);
   }
 
   void UnregisterExecutableMemoryChunk(MemoryChunk* chunk) {
+    base::MutexGuard guard(&executable_memory_mutex_);
     DCHECK_NE(executable_memory_.find(chunk), executable_memory_.end());
     executable_memory_.erase(chunk);
     chunk->heap()->UnregisterUnprotectedMemoryChunk(chunk);
@@ -396,6 +398,7 @@ class MemoryAllocator {
 
   // Data structure to remember allocated executable memory chunks.
   std::unordered_set<MemoryChunk*> executable_memory_;
+  base::Mutex executable_memory_mutex_;
 
   friend class heap::TestCodePageAllocatorScope;