diff --git a/ricepp/include/ricepp/codec.h b/ricepp/include/ricepp/codec.h
index 90b8d3ac..5105b8cc 100644
--- a/ricepp/include/ricepp/codec.h
+++ b/ricepp/include/ricepp/codec.h
@@ -130,7 +130,7 @@ class codec final {
 
   [[nodiscard]] size_t worst_case_bit_count(size_t pixel_count) const noexcept {
     static constexpr size_t const kFsBits{
-        std::countr_zero(pixel_traits::kBitCount)};
+        static_cast<size_t>(std::countr_zero(pixel_traits::kBitCount))};
     assert(pixel_count % kComponentStreamCount == 0);
     pixel_count /= kComponentStreamCount;
     size_t num = pixel_traits::kBitCount; // initial value
diff --git a/ricepp/include/ricepp/detail/decode.h b/ricepp/include/ricepp/detail/decode.h
index 5225c4e7..33a06d89 100644
--- a/ricepp/include/ricepp/detail/decode.h
+++ b/ricepp/include/ricepp/detail/decode.h
@@ -40,7 +40,8 @@ void decode_block(V block, BitstreamReader& reader, PixelTraits const& traits,
                   typename PixelTraits::value_type& last_value) {
   using pixel_value_type = typename PixelTraits::value_type;
   static constexpr unsigned kPixelBits{PixelTraits::kBitCount};
-  static constexpr unsigned kFsBits{std::countr_zero(kPixelBits)};
+  static constexpr unsigned kFsBits{
+      static_cast<unsigned>(std::countr_zero(kPixelBits))};
   static constexpr unsigned kFsMax{kPixelBits - 2};
 
   auto last = last_value;
diff --git a/ricepp/include/ricepp/detail/encode.h b/ricepp/include/ricepp/detail/encode.h
index 5854fee2..0fde4d85 100644
--- a/ricepp/include/ricepp/detail/encode.h
+++ b/ricepp/include/ricepp/detail/encode.h
@@ -91,7 +91,8 @@ void encode_block(V block, BitstreamWriter& writer, PixelTraits const& traits,
                   typename PixelTraits::value_type& last_value) {
   using pixel_value_type = typename PixelTraits::value_type;
   static constexpr unsigned kPixelBits{PixelTraits::kBitCount};
-  static constexpr unsigned kFsBits{std::countr_zero(kPixelBits)};
+  static constexpr unsigned kFsBits{
+      static_cast<unsigned>(std::countr_zero(kPixelBits))};
   static constexpr unsigned kFsMax{kPixelBits - 2};
   static constexpr pixel_value_type kPixelMsb{static_cast<pixel_value_type>(1)
                                               << (kPixelBits - 1)};