diff --git a/src/json.hpp b/src/json.hpp
index 3f0b6e3e9..ef55e2ead 100644
--- a/src/json.hpp
+++ b/src/json.hpp
@@ -3034,11 +3034,19 @@ class parser
         {
             case token_type::begin_object:
             {
-                if (keep and (not callback or ((keep = callback(depth++, parse_event_t::object_start, result)))))
+                if (keep)
                 {
-                    // explicitly set result to object to cope with {}
-                    result.m_type = value_t::object;
-                    result.m_value = value_t::object;
+                    if (callback)
+                    {
+                        keep = callback(depth++, parse_event_t::object_start, result);
+                    }
+
+                    if (not callback or keep)
+                    {
+                        // explicitly set result to object to cope with {}
+                        result.m_type = value_t::object;
+                        result.m_value = value_t::object;
+                    }
                 }
 
                 // read next token
@@ -3130,11 +3138,19 @@ class parser
 
             case token_type::begin_array:
             {
-                if (keep and (not callback or ((keep = callback(depth++, parse_event_t::array_start, result)))))
+                if (keep)
                 {
-                    // explicitly set result to object to cope with []
-                    result.m_type = value_t::array;
-                    result.m_value = value_t::array;
+                    if (callback)
+                    {
+                        keep = callback(depth++, parse_event_t::array_start, result);
+                    }
+
+                    if (not callback or keep)
+                    {
+                        // explicitly set result to array to cope with []
+                        result.m_type = value_t::array;
+                        result.m_value = value_t::array;
+                    }
                 }
 
                 // read next token
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 4ccbaf06d..b51aff76d 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -66,6 +66,19 @@ set_target_properties(catch_main PROPERTIES
 )
 target_include_directories(catch_main PRIVATE "thirdparty/catch")
 
+# https://stackoverflow.com/questions/2368811/how-to-set-warning-level-in-cmake
+if(MSVC)
+    # Force to always compile with W4
+    if(CMAKE_CXX_FLAGS MATCHES "/W[0-4]")
+        string(REGEX REPLACE "/W[0-4]" "/W4" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
+    else()
+        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /W4")
+    endif()
+
+    # Disable warning C4389: '==': signed/unsigned mismatch
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /wd4389")
+endif()
+
 #############################################################################
 # one executable for each unit test file
 #############################################################################
diff --git a/test/src/unit-udt.cpp b/test/src/unit-udt.cpp
index 6aa469fe4..409cac839 100644
--- a/test/src/unit-udt.cpp
+++ b/test/src/unit-udt.cpp
@@ -201,7 +201,7 @@ void from_json(const BasicJsonType& j, country& c)
     {
         {u8"中华人民共和国", country::china},
         {"France", country::france},
-        {"Российская Федерация", country::russia}
+        {u8"Российская Федерация", country::russia}
     };
 
     const auto it = m.find(str);