diff --git a/core/matrix/fbcsr.cpp b/core/matrix/fbcsr.cpp
index 00f93bf6351..5019a047923 100644
--- a/core/matrix/fbcsr.cpp
+++ b/core/matrix/fbcsr.cpp
@@ -342,7 +342,8 @@ void Fbcsr<ValueType, IndexType>::read(const mat_data &data)
     const index_type num_brows = detail::get_num_blocks(bs, data.size[0]);
 
     acc::range<acc::block_col_major<value_type, 3>> values(
-        std::array<size_type, 3>{blocks.size(), (size_type)bs, (size_type)bs},
+        std::array<size_type, 3>{blocks.size(), static_cast<size_type>(bs),
+                                 static_cast<size_type>(bs)},
         tmp->values_.get_data());
 
     for (auto it = blocks.begin(); it != blocks.end(); it++) {
diff --git a/reference/matrix/fbcsr_kernels.cpp b/reference/matrix/fbcsr_kernels.cpp
index a74753623f9..35c0bcbbf8b 100644
--- a/reference/matrix/fbcsr_kernels.cpp
+++ b/reference/matrix/fbcsr_kernels.cpp
@@ -79,7 +79,9 @@ void spmv(const std::shared_ptr<const ReferenceExecutor>,
     auto col_idxs = a->get_const_col_idxs();
     auto vals = a->get_const_values();
     const acc::range<acc::block_col_major<const ValueType, 3>> avalues{
-        std::array<size_type, 3>{nbnz, (size_type)bs, (size_type)bs}, vals};
+        std::array<size_type, 3>{nbnz, static_cast<size_type>(bs),
+                                 static_cast<size_type>(bs)},
+        vals};
 
     for (IndexType ibrow = 0; ibrow < nbrows; ++ibrow) {
         for (IndexType i = ibrow * bs * nvecs; i < (ibrow + 1) * bs * nvecs;