diff --git a/include/nlohmann/detail/output/binary_writer.hpp b/include/nlohmann/detail/output/binary_writer.hpp
index eb312e8a4..0a80d26b0 100644
--- a/include/nlohmann/detail/output/binary_writer.hpp
+++ b/include/nlohmann/detail/output/binary_writer.hpp
@@ -863,7 +863,7 @@ class binary_writer
     {
         std::size_t array_index = 0ul;
 
-        const std::size_t embedded_document_size = std::accumulate(std::begin(value), std::end(value), 0ul, [&array_index](std::size_t result, const typename BasicJsonType::array_t::value_type & el)
+        const std::size_t embedded_document_size = std::accumulate(std::begin(value), std::end(value), std::size_t(0), [&array_index](std::size_t result, const typename BasicJsonType::array_t::value_type & el)
         {
             return result + calc_bson_element_size(std::to_string(array_index++), el);
         });
@@ -984,7 +984,7 @@ class binary_writer
     */
     static std::size_t calc_bson_object_size(const typename BasicJsonType::object_t& value)
     {
-        std::size_t document_size = std::accumulate(value.begin(), value.end(), 0ul,
+        std::size_t document_size = std::accumulate(value.begin(), value.end(), std::size_t(0),
                                     [](size_t result, const typename BasicJsonType::object_t::value_type & el)
         {
             return result += calc_bson_element_size(el.first, el.second);
diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
index 06da81532..e2a68e6f5 100644
--- a/single_include/nlohmann/json.hpp
+++ b/single_include/nlohmann/json.hpp
@@ -12155,7 +12155,7 @@ class binary_writer
     {
         std::size_t array_index = 0ul;
 
-        const std::size_t embedded_document_size = std::accumulate(std::begin(value), std::end(value), 0ul, [&array_index](std::size_t result, const typename BasicJsonType::array_t::value_type & el)
+        const std::size_t embedded_document_size = std::accumulate(std::begin(value), std::end(value), std::size_t(0), [&array_index](std::size_t result, const typename BasicJsonType::array_t::value_type & el)
         {
             return result + calc_bson_element_size(std::to_string(array_index++), el);
         });
@@ -12276,7 +12276,7 @@ class binary_writer
     */
     static std::size_t calc_bson_object_size(const typename BasicJsonType::object_t& value)
     {
-        std::size_t document_size = std::accumulate(value.begin(), value.end(), 0ul,
+        std::size_t document_size = std::accumulate(value.begin(), value.end(), std::size_t(0),
                                     [](size_t result, const typename BasicJsonType::object_t::value_type & el)
         {
             return result += calc_bson_element_size(el.first, el.second);
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index df2f055bf..8769c6b9d 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -87,11 +87,9 @@ if(MSVC)
         set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /W4")
     endif()
 
-    # Disable warning C4389: '==': signed/unsigned mismatch
-	# Disable warning C4309: 'static_cast': truncation of constant value
 	# Disable warning C4566: character represented by universal-character-name '\uFF01' cannot be represented in the current code page (1252)
 	# Disable warning C4996: 'nlohmann::basic_json<std::map,std::vector,std::string,bool,int64_t,uint64_t,double,std::allocator,nlohmann::adl_serializer>::operator <<': was declared deprecated
-    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /wd4389 /wd4309 /wd4566 /wd4996")
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /wd4566 /wd4996")
 
 	# https://github.com/nlohmann/json/issues/1114
 	set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} /bigobj")