diff --git a/CMakeLists.txt b/CMakeLists.txt
index ad4b7e902..dcb9cd677 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -15,7 +15,7 @@ else()
 endif()
 
 if(MSVC)
-    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /bigobj")
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /bigobj /W3 /WX")
 else()
     set(CMAKE_CXX_FLAGS "-Wall -g -Wextra -Wshadow -pedantic -Wold-style-cast ${CMAKE_CXX_FLAGS}")
     option(WITH_WERROR "Compile with '-Werror' C++ compiler flag" ON)
diff --git a/unittests/complex.hpp b/unittests/complex.hpp
index 1f2387900..ebd7e357a 100644
--- a/unittests/complex.hpp
+++ b/unittests/complex.hpp
@@ -69,8 +69,8 @@ void test_complex()
     CHECK_EQ( o_float, i_float );
     CHECK_EQ( o_double.real(), doctest::Approx(i_double.real()).epsilon(1e-5) );
     CHECK_EQ( o_double.imag(), doctest::Approx(i_double.imag()).epsilon(1e-5) );
-    CHECK_EQ( o_ldouble.real(), doctest::Approx(i_ldouble.real()).epsilon(1e-5) );
-    CHECK_EQ( o_ldouble.imag(), doctest::Approx(i_ldouble.imag()).epsilon(1e-5) );
+    CHECK_EQ( o_ldouble.real(), doctest::Approx(i_ldouble.real()).epsilon(1e-5L) );
+    CHECK_EQ( o_ldouble.imag(), doctest::Approx(i_ldouble.imag()).epsilon(1e-5L) );
   }
 }