diff --git a/src/windows-emulator/emulator_thread.hpp b/src/windows-emulator/emulator_thread.hpp
index 0a646092..eab80c8c 100644
--- a/src/windows-emulator/emulator_thread.hpp
+++ b/src/windows-emulator/emulator_thread.hpp
@@ -10,7 +10,7 @@ struct process_context;
 
 struct pending_apc
 {
-    ULONG flags{};
+    uint32_t flags{};
     uint64_t apc_routine{};
     uint64_t apc_argument1{};
     uint64_t apc_argument2{};
diff --git a/src/windows-emulator/process_context.cpp b/src/windows-emulator/process_context.cpp
index f604eacd..bb720ec4 100644
--- a/src/windows-emulator/process_context.cpp
+++ b/src/windows-emulator/process_context.cpp
@@ -119,6 +119,7 @@ void process_context::setup(x64_emulator& emu, memory_manager& memory, const app
     this->ntdll_image_base = ntdll.image_base;
     this->ldr_initialize_thunk = ntdll.find_export("LdrInitializeThunk");
     this->rtl_user_thread_start = ntdll.find_export("RtlUserThreadStart");
+    this->ki_user_apc_dispatcher = ntdll.find_export("KiUserApcDispatcher");
     this->ki_user_exception_dispatcher = ntdll.find_export("KiUserExceptionDispatcher");
 
     this->default_register_set = emu.save_registers();
@@ -139,6 +140,7 @@ void process_context::serialize(utils::buffer_serializer& buffer) const
     buffer.write(this->ntdll_image_base);
     buffer.write(this->ldr_initialize_thunk);
     buffer.write(this->rtl_user_thread_start);
+    buffer.write(this->ki_user_apc_dispatcher);
     buffer.write(this->ki_user_exception_dispatcher);
 
     buffer.write(this->events);
@@ -173,6 +175,7 @@ void process_context::deserialize(utils::buffer_deserializer& buffer)
     buffer.read(this->ntdll_image_base);
     buffer.read(this->ldr_initialize_thunk);
     buffer.read(this->rtl_user_thread_start);
+    buffer.read(this->ki_user_apc_dispatcher);
     buffer.read(this->ki_user_exception_dispatcher);
 
     buffer.read(this->events);
diff --git a/src/windows-emulator/process_context.hpp b/src/windows-emulator/process_context.hpp
index f01647b4..1be428b3 100644
--- a/src/windows-emulator/process_context.hpp
+++ b/src/windows-emulator/process_context.hpp
@@ -75,6 +75,7 @@ struct process_context
     uint64_t ntdll_image_base{};
     uint64_t ldr_initialize_thunk{};
     uint64_t rtl_user_thread_start{};
+    uint64_t ki_user_apc_dispatcher{};
     uint64_t ki_user_exception_dispatcher{};
 
     handle_store<handle_types::event, event> events{};
diff --git a/src/windows-emulator/syscalls.cpp b/src/windows-emulator/syscalls.cpp
index 480b4834..5675d0da 100644
--- a/src/windows-emulator/syscalls.cpp
+++ b/src/windows-emulator/syscalls.cpp
@@ -292,7 +292,7 @@ namespace syscalls
     NTSTATUS handle_NtGetCurrentProcessorNumberEx(const syscall_context&,
                                                   emulator_object<PROCESSOR_NUMBER> processor_number);
     NTSTATUS handle_NtQueueApcThreadEx2(const syscall_context& c, handle thread_handle, handle reserve_handle,
-                                        ULONG apc_flags, uint64_t apc_routine, uint64_t apc_argument1,
+                                        uint32_t apc_flags, uint64_t apc_routine, uint64_t apc_argument1,
                                         uint64_t apc_argument2, uint64_t apc_argument3);
 
     // syscalls/timer.cpp:
diff --git a/src/windows-emulator/syscalls/thread.cpp b/src/windows-emulator/syscalls/thread.cpp
index 25ebd1ba..3c7a90b5 100644
--- a/src/windows-emulator/syscalls/thread.cpp
+++ b/src/windows-emulator/syscalls/thread.cpp
@@ -565,7 +565,7 @@ namespace syscalls
     }
 
     NTSTATUS handle_NtQueueApcThreadEx2(const syscall_context& c, const handle thread_handle,
-                                        const handle /*reserve_handle*/, const ULONG apc_flags,
+                                        const handle /*reserve_handle*/, const uint32_t apc_flags,
                                         const uint64_t apc_routine, const uint64_t apc_argument1,
                                         const uint64_t apc_argument2, const uint64_t apc_argument3)
     {
@@ -576,6 +576,13 @@ namespace syscalls
             return STATUS_INVALID_HANDLE;
         }
 
+        if (apc_flags)
+        {
+            c.win_emu.log.error("Unsupported APC flags: %X\n", apc_flags);
+            c.emu.stop();
+            return STATUS_NOT_SUPPORTED;
+        }
+
         thread->pending_apcs.push_back({
             .flags = apc_flags,
             .apc_routine = apc_routine,