diff --git a/modules/dnn/src/layers/mvn_layer.cpp b/modules/dnn/src/layers/mvn_layer.cpp
index d59e339ac4..9c8bdf5106 100644
--- a/modules/dnn/src/layers/mvn_layer.cpp
+++ b/modules/dnn/src/layers/mvn_layer.cpp
@@ -171,7 +171,9 @@ public:
             String buildopt = "-DNUM=4" + opts;
             ocl::Kernel k("mean_fuse4", ocl::dnn::mvn_oclsrc, buildopt + " -DKERNEL_MEAN_FUSE");
             size_t localsize[] = { LOCAL_SIZE };
-            size_t globalsize[] = { (size_t)s[0] / 4 * localsize[0] };
+            size_t groups = std::max<size_t>(1, s[0] / 4);
+            size_t globalsize[] = { groups * localsize[0] };
+
 
             int argId = 0;
             k.set(argId++, ocl::KernelArg::PtrReadOnly(inpMat));
@@ -374,7 +376,7 @@ public:
                            const std::vector<MatShape> &outputs) const CV_OVERRIDE
     {
         CV_UNUSED(outputs); // suppress unused variable warning
-        long flops = 0;
+        int64 flops = 0;
         for(int i = 0; i < inputs.size(); i++)
         {
             flops += 6*total(inputs[i]) + 3*total(inputs[i], 0, normVariance ? 2 : 1);