diff --git a/number_theory/test_math_functions.cpp b/number_theory/test_math_functions.cpp
index 5a6dcde..ef790aa 100644
--- a/number_theory/test_math_functions.cpp
+++ b/number_theory/test_math_functions.cpp
@@ -510,7 +510,7 @@ template <class IntType>
     std::atomic_flag result = ATOMIC_FLAG_INIT;
     for (size_t i = 0; i < kTotalThreads; ++i) {
         threads.emplace_back([thread_id = i, &result
-#if defined(_MSC_VER)
+#if defined(_MSC_VER) && !defined(__clang__)
                               ,
                               kTestsPerThread
 #endif
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 6dd7881..f71c524 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -31,6 +31,7 @@ if (USING_MINGW_GCC)
 endif()
 
 set(LINK_THREADS_LIBRARY_MANUALLY False)
+set(LINK_COMPILER_RT_BUILTINS_MANUALLY False)
 
 
 if (CMAKE_SYSTEM_NAME MATCHES "Linux")
@@ -249,6 +250,7 @@ function(configure_msvc_or_clang_msvc_options)
             ${LOCAL_FN_TEST_CXX_COMPILE_OPTIONS}
             "/W4" # Enable -Wall and -Wextra
         )
+        set(LINK_COMPILER_RT_BUILTINS_MANUALLY True PARENT_SCOPE)
     else()
         if (MSVC_VERSION GREATER_EQUAL 1914)
             set(LOCAL_FN_TEST_CXX_COMPILE_OPTIONS
@@ -391,49 +393,47 @@ if (NOT USING_MINGW_GCC_32)
     list(APPEND TestOptionalDependencies "")
     list(APPEND TestIsCProject False)
 
-    if (NOT (CMAKE_CXX_COMPILER_ID STREQUAL "Clang" AND CMAKE_CXX_COMPILER_FRONTEND_VARIANT STREQUAL "MSVC"))
-        list(APPEND TestFilenames "test_integers_128_bit.cpp")
-        list(APPEND TestDirectories "number_theory")
-        list(APPEND TestLangVersions "17 20 23 26")
-        list(APPEND TestDependencies "")
-        list(APPEND TestOptionalDependencies "")
-        list(APPEND TestIsCProject False)
+    list(APPEND TestFilenames "test_integers_128_bit.cpp")
+    list(APPEND TestDirectories "number_theory")
+    list(APPEND TestLangVersions "17 20 23 26")
+    list(APPEND TestDependencies "")
+    list(APPEND TestOptionalDependencies "")
+    list(APPEND TestIsCProject False)
 
-        list(APPEND TestFilenames "test_math_functions.cpp")
-        list(APPEND TestDirectories "number_theory")
-        list(APPEND TestLangVersions "17 20 23 26")
-        list(APPEND TestDependencies "")
-        if ((CMAKE_CXX_COMPILER_ID STREQUAL "GNU" OR CMAKE_CXX_COMPILER_FRONTEND_VARIANT STREQUAL "GNU") AND NOT APPLE)
-            list(APPEND TestOptionalDependencies "mpfr")
-        else()
-            list(APPEND TestOptionalDependencies "")
-        endif()
-        list(APPEND TestIsCProject False)
+    list(APPEND TestFilenames "test_math_functions.cpp")
+    list(APPEND TestDirectories "number_theory")
+    list(APPEND TestLangVersions "17 20 23 26")
+    list(APPEND TestDependencies "")
+    if (LINUX)
+        list(APPEND TestOptionalDependencies "mpfr")
+    else()
+        list(APPEND TestOptionalDependencies "")
     endif()
+    list(APPEND TestIsCProject False)
 
-    if (CMAKE_CXX_COMPILER_ID STREQUAL "GNU" OR CMAKE_CXX_COMPILER_FRONTEND_VARIANT STREQUAL "GNU")
-        list(APPEND TestFilenames "test_is_prime_bpsw.cpp")
-        list(APPEND TestDirectories "number_theory")
-        list(APPEND TestLangVersions "17 20 23 26")
-        list(APPEND TestDependencies "")
-        if (NOT APPLE)
-            list(APPEND TestOptionalDependencies "gmp")
-        else()
-            list(APPEND TestOptionalDependencies "")
-        endif()
-        list(APPEND TestIsCProject False)
+    list(APPEND TestFilenames "test_is_prime_bpsw.cpp")
+    list(APPEND TestDirectories "number_theory")
+    list(APPEND TestLangVersions "17 20 23 26")
+    list(APPEND TestDependencies "")
+    if (LINUX)
+        list(APPEND TestOptionalDependencies "gmp")
+    else()
+        list(APPEND TestOptionalDependencies "")
+    endif()
+    list(APPEND TestIsCProject False)
 
-        list(APPEND TestFilenames "test_kronecker_symbol.cpp")
-        list(APPEND TestDirectories "number_theory")
-        list(APPEND TestLangVersions "17 20 23 26")
-        list(APPEND TestDependencies "")
-        if (NOT APPLE)
-            list(APPEND TestOptionalDependencies "gmp gmpxx")
-        else()
-            list(APPEND TestOptionalDependencies "")
-        endif()
-        list(APPEND TestIsCProject False)
+    list(APPEND TestFilenames "test_kronecker_symbol.cpp")
+    list(APPEND TestDirectories "number_theory")
+    list(APPEND TestLangVersions "17 20 23 26")
+    list(APPEND TestDependencies "")
+    if (LINUX)
+        list(APPEND TestOptionalDependencies "gmp gmpxx")
+    else()
+        list(APPEND TestOptionalDependencies "")
+    endif()
+    list(APPEND TestIsCProject False)
 
+    if (CMAKE_CXX_COMPILER_ID STREQUAL "GNU" OR CMAKE_CXX_COMPILER_FRONTEND_VARIANT STREQUAL "GNU")
         list(APPEND TestFilenames "test_long_int.cpp")
         list(APPEND TestDirectories "number_theory")
         list(APPEND TestLangVersions "17 20 23 26")
@@ -603,6 +603,10 @@ function(
         target_link_libraries(${target} PUBLIC Threads::Threads)
     endif()
 
+    if (LINK_COMPILER_RT_BUILTINS_MANUALLY)
+        target_link_libraries(${target} PUBLIC clang_rt.builtins-x86_64)
+    endif()
+
     if (USING_MINGW_GCC AND NOT WIN32)
         target_link_options(${target} PUBLIC -static -static-libgcc -static-libstdc++)
     endif()
diff --git a/tests/run_windows_msys2_mingw_64_tests.bat b/tests/run_windows_msys2_mingw_64_tests.bat
index 6030e72..2c06b3e 100644
--- a/tests/run_windows_msys2_mingw_64_tests.bat
+++ b/tests/run_windows_msys2_mingw_64_tests.bat
@@ -8,7 +8,9 @@ copy "..\tf_idf_actrie\Anglo_Saxon_Chronicle.txt" ".\%build_dir%\Anglo_Saxon_Chr
 
 cd ".\%build_dir%"
 
-cmake -G "MSYS Makefiles" -DCMAKE_BUILD_TYPE=RelWithDebInfo -S .. -B .
+@REM "MSYS Makefiles" - may use clang-cl instead of gcc / clang
+@REM "MinGW Makefiles" - may use clang-cl instead of gcc / clang
+cmake -G "Unix Makefiles" -DCMAKE_BUILD_TYPE=RelWithDebInfo -S .. -B .
 if %errorlevel% neq 0 exit /b %errorlevel%
 
 make all --jobs %NUMBER_OF_PROCESSORS%