diff --git a/include/iwa/swapchain.hpp b/include/iwa/swapchain.hpp
index 7a1a1c2..690f094 100644
--- a/include/iwa/swapchain.hpp
+++ b/include/iwa/swapchain.hpp
@@ -34,6 +34,7 @@ private:
 
     std::uint32_t mCurrentImageIdx = INVALID_IMAGE_INDEX;
     unsigned mCurrentFrameIdx = 0;
+    unsigned mCurrentSemaphoreIdx = 0;
     ObjectPtr<Window> mWindow;
     std::vector<ObjectPtr<Image>> mImages;
     std::vector<ObjectPtr<Semaphore>> mImageAvailableSemaphores;
@@ -45,8 +46,8 @@ public:
     ~Swapchain() noexcept override;
 
     [[nodiscard]] const ObjectPtr<Window>& getWindow() const noexcept { return mWindow; }
-    [[nodiscard]] std::size_t getNumParallelFrames() const noexcept { return mImageAvailableSemaphores.size(); }
-    [[nodiscard]] const ObjectPtr<Semaphore>& getCurrentAvailableSemaphore() const noexcept { return mImageAvailableSemaphores[mCurrentFrameIdx]; }
+    [[nodiscard]] std::size_t getNumParallelFrames() const noexcept { return mImageAvailableSemaphores.size() - 1; }
+    [[nodiscard]] const ObjectPtr<Semaphore>& getCurrentAvailableSemaphore() const noexcept { return mImageAvailableSemaphores[mCurrentSemaphoreIdx]; }
     [[nodiscard]] unsigned getCurrentFrameIdx() const noexcept { return mCurrentFrameIdx; }
     [[nodiscard]] const std::vector<ObjectPtr<Image>>& getImages() const noexcept { return mImages; }
     [[nodiscard]] std::uint32_t getCurrentImageIdx() const noexcept { return mCurrentImageIdx; }
diff --git a/source/swapchain.cpp b/source/swapchain.cpp
index 79afe4b..f9f9bce 100644
--- a/source/swapchain.cpp
+++ b/source/swapchain.cpp
@@ -97,8 +97,9 @@ Swapchain::Swapchain(ObjectPtr<Device> owner, SwapchainCreationArgs args)
         : super_t(std::move(owner)), mWindow(std::move(args.window)), mImageUsage(args.imageUsage)
 {
     MIJIN_ASSERT(mWindow, "Invalid SwapchainCreationArgs: window cannot be NULL.");
+    MIJIN_ASSERT_FATAL(args.parallelFrames > 0, "Invalid SwapchainCreationArgs: parallelFrames must be > 0.");
 
-    mImageAvailableSemaphores.resize(args.parallelFrames);
+    mImageAvailableSemaphores.resize(args.parallelFrames - 1);
     recreate();
 }
 Swapchain::~Swapchain() noexcept
@@ -131,6 +132,8 @@ mijin::Task<> Swapchain::c_present(const PresentArgs& args)
 
     // next image, please
     mCurrentFrameIdx = (mCurrentFrameIdx + 1) % static_cast<int>(getNumParallelFrames());
+    mCurrentSemaphoreIdx = (mCurrentSemaphoreIdx + 1) % static_cast<int>(mImageAvailableSemaphores.size());
+    // logMsg("frame: {}, semaphore: {}", mCurrentFrameIdx, mCurrentSemaphoreIdx);
     if (result == vk::Result::eSuccess) {
         co_await c_acquireImage();
     }
@@ -280,7 +283,7 @@ void Swapchain::acquireImage()
 
     try
     {
-        const vk::ResultValue<std::uint32_t> result = getOwner()->getVkHandle().acquireNextImageKHR(mHandle, std::numeric_limits<std::uint64_t>::max(), *mImageAvailableSemaphores[mCurrentFrameIdx]);
+        const vk::ResultValue<std::uint32_t> result = getOwner()->getVkHandle().acquireNextImageKHR(mHandle, std::numeric_limits<std::uint64_t>::max(), *getCurrentAvailableSemaphore());
         if (result.result != vk::Result::eSuccess)
         {
             assert(result.result == vk::Result::eSuboptimalKHR);
@@ -302,7 +305,7 @@ mijin::Task<> Swapchain::c_acquireImage()
         vk::ResultValue<std::uint32_t> result = vk::ResultValue<std::uint32_t>(vk::Result::eTimeout, 0);
         while(true)
         {
-            result = getOwner()->getVkHandle().acquireNextImageKHR(mHandle, 0, *mImageAvailableSemaphores[mCurrentFrameIdx]);
+            result = getOwner()->getVkHandle().acquireNextImageKHR(mHandle, 0, *getCurrentAvailableSemaphore());
             if (result.result != vk::Result::eTimeout && result.result != vk::Result::eNotReady) {
                 break;
             }