diff --git a/modules/v4d/include/opencv2/v4d/detail/framebuffercontext.hpp b/modules/v4d/include/opencv2/v4d/detail/framebuffercontext.hpp
index d30087131..3f7d2f31b 100644
--- a/modules/v4d/include/opencv2/v4d/detail/framebuffercontext.hpp
+++ b/modules/v4d/include/opencv2/v4d/detail/framebuffercontext.hpp
@@ -115,7 +115,7 @@ class CV_EXPORTS FrameBufferContext {
     int index_;
 
     void* currentSyncObject_ = 0;
-    bool firstSync_ = true;
+    static bool firstSync_;
 public:
     /*!
      * Acquires and releases the framebuffer from and to OpenGL.
diff --git a/modules/v4d/include/opencv2/v4d/util.hpp b/modules/v4d/include/opencv2/v4d/util.hpp
index 407ab72ad..78fa00e1d 100644
--- a/modules/v4d/include/opencv2/v4d/util.hpp
+++ b/modules/v4d/include/opencv2/v4d/util.hpp
@@ -85,11 +85,7 @@ void run_sync_on_main(std::function<void()> fn) {
     sync_run = true;
 
 #ifdef __EMSCRIPTEN__
-    typedef void* function_t( void* ) ;
-    function_t* ptr_fun = fn.target<function_t>() ;
-    //Check that the function object wrapped something callable
-    CV_Assert( ptr_fun != nullptr );
-    emscripten_sync_run_in_main_runtime_thread(EM_FUNC_SIG_V, ptr_fun);
+    emscripten_sync_run_in_main_runtime_thread(EM_FUNC_SIG_V, cv::v4d::detail::get_fn_ptr<Tid>(fn));
 #else
     fn();
 #endif
diff --git a/modules/v4d/include/opencv2/v4d/v4d.hpp b/modules/v4d/include/opencv2/v4d/v4d.hpp
index e305ad29a..99f7029f0 100644
--- a/modules/v4d/include/opencv2/v4d/v4d.hpp
+++ b/modules/v4d/include/opencv2/v4d/v4d.hpp
@@ -271,11 +271,8 @@ public:
      * This function main purpose is to abstract the run loop for portability reasons.
      * @param fn A functor that will be called repeatetly until the application terminates or the functor returns false
      */
-    CV_EXPORTS void run(std::function<bool(cv::Ptr<V4D>)> fn
-#ifndef __EMSCRIPTEN__
-            , size_t workers = 0
-#endif
-    );
+
+    CV_EXPORTS void run(std::function<bool(cv::Ptr<V4D>)> fn, size_t workers = 0);
     /*!
      * Called to feed an image directly to the framebuffer
      */
diff --git a/modules/v4d/samples/cube-demo.cpp b/modules/v4d/samples/cube-demo.cpp
index 78585227f..a95ef2915 100644
--- a/modules/v4d/samples/cube-demo.cpp
+++ b/modules/v4d/samples/cube-demo.cpp
@@ -26,12 +26,12 @@ using std::cerr;
 using std::endl;
 
 /* OpenGL constants and variables */
-static thread_local const unsigned int triangles = 12;
-static thread_local const unsigned int vertices_index = 0;
-static thread_local const unsigned int colors_index = 1;
-static thread_local unsigned int shader_program;
-static thread_local unsigned int vao;
-static thread_local unsigned int uniform_transform;
+static const unsigned int triangles = 12;
+static const unsigned int vertices_index = 0;
+static const unsigned int colors_index = 1;
+static unsigned int shader_program;
+static unsigned int vao;
+static unsigned int uniform_transform;
 
 cv::Ptr<cv::v4d::V4D> global_v4d;
 //Simple transform & pass-through shaders
@@ -198,9 +198,9 @@ static void render_scene() {
 #ifndef __EMSCRIPTEN__
 //applies a glow effect to an image
 static void glow_effect(const cv::UMat& src, cv::UMat& dst, const int ksize) {
-    static thread_local cv::UMat resize;
-    static thread_local cv::UMat blur;
-    static thread_local cv::UMat dst16;
+    cv::UMat resize;
+    cv::UMat blur;
+    cv::UMat dst16;
 
     cv::bitwise_not(src, dst);
 
diff --git a/modules/v4d/src/detail/framebuffercontext.cpp b/modules/v4d/src/detail/framebuffercontext.cpp
index d9f82ca12..f81ee5da1 100644
--- a/modules/v4d/src/detail/framebuffercontext.cpp
+++ b/modules/v4d/src/detail/framebuffercontext.cpp
@@ -19,12 +19,14 @@
 
 namespace cv {
 namespace v4d {
+
 namespace detail {
 
 static void glfw_error_callback(int error, const char* description) {
     fprintf(stderr, "GLFW Error: (%d) %s\n", error, description);
 }
 
+bool FrameBufferContext::firstSync_ = true;
 
 int frameBufferContextCnt = 0;
 
@@ -700,7 +702,7 @@ void FrameBufferContext::begin(GLenum framebufferTarget) {
 void FrameBufferContext::end() {
     this->makeCurrent();
     GL_CHECK(glFlush());
-    //    this->fence();
+//    this->fence();
 }
 
 void FrameBufferContext::download(cv::UMat& m) {
diff --git a/modules/v4d/src/util.cpp b/modules/v4d/src/util.cpp
index 931cdfcc8..2b4cafdbb 100644
--- a/modules/v4d/src/util.cpp
+++ b/modules/v4d/src/util.cpp
@@ -482,7 +482,7 @@ public:
                 );
             );
             GL_CHECK(glFramebufferTexture2D(GL_READ_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, texture, 0));
-            cv::Size fbSz = window_->framebufferSize();
+            cv::Size fbSz = window_->fbSize();
             window_->fbCtx().blitFrameBufferToFrameBuffer(cv::Rect(0, 0, width_, height_), cv::Size(width_, height_), window_->fbCtx().getFramebufferID(), true, true);
 
             return true;
diff --git a/modules/v4d/src/v4d.cpp b/modules/v4d/src/v4d.cpp
index a9265fa93..8a946d6d6 100644
--- a/modules/v4d/src/v4d.cpp
+++ b/modules/v4d/src/v4d.cpp
@@ -193,12 +193,7 @@ static void do_frame(void* void_fn_ptr) {
 
 static bool first_run = true;
 
-void V4D::run(std::function<bool(cv::Ptr<V4D>)> fn
-#ifndef __EMSCRIPTEN__
-        , size_t workers
-#endif
-        ) {
-#ifndef __EMSCRIPTEN__
+void V4D::run(std::function<bool(cv::Ptr<V4D>)> fn, size_t workers) {
     numWorkers_ = workers;
     std::vector<std::thread*> threads;
     {
@@ -246,7 +241,6 @@ void V4D::run(std::function<bool(cv::Ptr<V4D>)> fn
             }
         }
     }
-#endif
 
     this->makeCurrent();
 #ifndef __EMSCRIPTEN__
@@ -271,10 +265,8 @@ void V4D::run(std::function<bool(cv::Ptr<V4D>)> fn
 
     if(this->isMain()) {
         thread_pool_.finish();
-#ifndef __EMSCRIPTEN__
         for(auto& t : threads)
             t->join();
-#endif
     }
 }