diff --git a/thread/thread.cpp b/thread/thread.cpp
index 69335aec..4a105262 100644
--- a/thread/thread.cpp
+++ b/thread/thread.cpp
@@ -130,10 +130,17 @@ namespace photon
         free(ptr);
     }
 
-    Delegate<void*, size_t> photon_thread_alloc(
-        &default_photon_thread_stack_alloc, nullptr);
-    Delegate<void, void*, size_t> photon_thread_dealloc(
-        &default_photon_thread_stack_dealloc, nullptr);
+    Delegate<void *, size_t> &photon_thread_alloc() {
+        static Delegate<void *, size_t> _photon_thread_alloc(
+            &default_photon_thread_stack_alloc, nullptr);
+        return _photon_thread_alloc;
+    }
+
+    Delegate<void, void *, size_t> &photon_thread_dealloc() {
+        static Delegate<void, void *, size_t> _photon_thread_dealloc(
+            &default_photon_thread_stack_dealloc, nullptr);
+        return _photon_thread_dealloc;
+    }
 
     struct vcpu_t;
     struct thread;
@@ -283,7 +290,7 @@ namespace photon
             assert(state == states::DONE);
             // `buf` and `stack_size` will always store on register
             // when calling deallocating.
-            photon_thread_dealloc(buf, stack_size);
+            photon_thread_dealloc()(buf, stack_size);
         }
     };
 
@@ -838,7 +845,7 @@ R"(
             LOG_ERROR_RETURN(ENOSYS, nullptr, "Photon not initialized in this vCPU (OS thread)");
         size_t randomizer = (rand() % 32) * (1024 + 8);
         stack_size = align_up(randomizer + stack_size + sizeof(thread), PAGE_SIZE);
-        char* ptr = (char*)photon_thread_alloc(stack_size);
+        char *ptr = (char *)photon_thread_alloc()(stack_size);
         auto p = ptr + stack_size - sizeof(thread) - randomizer;
         (uint64_t&)p &= ~63;
         auto th = new (p) thread;
@@ -1808,6 +1815,13 @@ R"(
         return --_n_vcpu;
     }
 
+    void set_photon_thread_stack_allocator(
+        Delegate<void *, size_t> _photon_thread_alloc,
+        Delegate<void, void *, size_t> _photon_thread_dealloc) {
+        photon_thread_alloc() = _photon_thread_alloc;
+        photon_thread_dealloc() = _photon_thread_dealloc;
+    }
+
     void* stackful_malloc(size_t size) {
         return CURRENT->stackful_malloc(size);
     }