diff --git a/.github/workflows/cmake.yml b/.github/workflows/cmake.yml
index 2d0b88f..7167c09 100644
--- a/.github/workflows/cmake.yml
+++ b/.github/workflows/cmake.yml
@@ -58,9 +58,15 @@
     - name: Test
       working-directory: ${{github.workspace}}/build
       shell: bash
-      run: if [ "${{ matrix.os }}" == "windows-latest" ]; then cd ${{ matrix.type }}; fi; ./utest_test 
+      run: if [ "${{ matrix.os }}" == "windows-latest" ]; then cd ${{ matrix.type }}; fi; ./utest_test
 
     - name: Test Whole Program Optimization
       working-directory: ${{github.workspace}}/build
       shell: bash
-      run: if [ "${{ matrix.os }}" == "windows-latest" ]; then cd ${{ matrix.type }}; fi; ./utest_test_wpo 
+      run: if [ "${{ matrix.os }}" == "windows-latest" ]; then cd ${{ matrix.type }}; fi; ./utest_test_wpo
+
+    - name: Test with Multithreading
+      working-directory: ${{github.workspace}}/build
+      shell: bash
+      if: startsWith(matrix.os, 'windows')
+      run: if [ "${{ matrix.os }}" == "windows-latest" ]; then cd ${{ matrix.type }}; fi; ./utest_test_mt

diff --git a/.github/workflows/cmake.yml b/.github/workflows/cmake.yml
index 2d0b88f..7167c09 100644
--- a/.github/workflows/cmake.yml
+++ b/.github/workflows/cmake.yml
@@ -58,9 +58,15 @@
     - name: Test
       working-directory: ${{github.workspace}}/build
       shell: bash
-      run: if [ "${{ matrix.os }}" == "windows-latest" ]; then cd ${{ matrix.type }}; fi; ./utest_test 
+      run: if [ "${{ matrix.os }}" == "windows-latest" ]; then cd ${{ matrix.type }}; fi; ./utest_test
 
     - name: Test Whole Program Optimization
       working-directory: ${{github.workspace}}/build
       shell: bash
-      run: if [ "${{ matrix.os }}" == "windows-latest" ]; then cd ${{ matrix.type }}; fi; ./utest_test_wpo 
+      run: if [ "${{ matrix.os }}" == "windows-latest" ]; then cd ${{ matrix.type }}; fi; ./utest_test_wpo
+
+    - name: Test with Multithreading
+      working-directory: ${{github.workspace}}/build
+      shell: bash
+      if: startsWith(matrix.os, 'windows')
+      run: if [ "${{ matrix.os }}" == "windows-latest" ]; then cd ${{ matrix.type }}; fi; ./utest_test_mt
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index c27da2a..028300f 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -144,3 +144,20 @@
   target_compile_options(utest_test_wpo PRIVATE "$<$<CONFIG:RELEASE>:/GL>")
   target_link_options(utest_test_wpo PRIVATE "$<$<CONFIG:RELEASE>:/LTCG>")
 endif()
+
+if("${CMAKE_CXX_COMPILER_ID}" STREQUAL "MSVC")
+  add_executable(utest_test_mt
+    ../utest.h
+    main.c
+    test.c
+    test11.c
+    test99.c
+    test.cpp
+    test11.cpp
+    stdint_include.c
+    type_printers.c
+    type_printers.cpp
+  )
+
+  target_compile_definitions(utest_test_mt PUBLIC "/MT")
+endif()

diff --git a/.github/workflows/cmake.yml b/.github/workflows/cmake.yml
index 2d0b88f..7167c09 100644
--- a/.github/workflows/cmake.yml
+++ b/.github/workflows/cmake.yml
@@ -58,9 +58,15 @@
     - name: Test
       working-directory: ${{github.workspace}}/build
       shell: bash
-      run: if [ "${{ matrix.os }}" == "windows-latest" ]; then cd ${{ matrix.type }}; fi; ./utest_test 
+      run: if [ "${{ matrix.os }}" == "windows-latest" ]; then cd ${{ matrix.type }}; fi; ./utest_test
 
     - name: Test Whole Program Optimization
       working-directory: ${{github.workspace}}/build
       shell: bash
-      run: if [ "${{ matrix.os }}" == "windows-latest" ]; then cd ${{ matrix.type }}; fi; ./utest_test_wpo 
+      run: if [ "${{ matrix.os }}" == "windows-latest" ]; then cd ${{ matrix.type }}; fi; ./utest_test_wpo
+
+    - name: Test with Multithreading
+      working-directory: ${{github.workspace}}/build
+      shell: bash
+      if: startsWith(matrix.os, 'windows')
+      run: if [ "${{ matrix.os }}" == "windows-latest" ]; then cd ${{ matrix.type }}; fi; ./utest_test_mt
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index c27da2a..028300f 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -144,3 +144,20 @@
   target_compile_options(utest_test_wpo PRIVATE "$<$<CONFIG:RELEASE>:/GL>")
   target_link_options(utest_test_wpo PRIVATE "$<$<CONFIG:RELEASE>:/LTCG>")
 endif()
+
+if("${CMAKE_CXX_COMPILER_ID}" STREQUAL "MSVC")
+  add_executable(utest_test_mt
+    ../utest.h
+    main.c
+    test.c
+    test11.c
+    test99.c
+    test.cpp
+    test11.cpp
+    stdint_include.c
+    type_printers.c
+    type_printers.cpp
+  )
+
+  target_compile_definitions(utest_test_mt PUBLIC "/MT")
+endif()
diff --git a/utest.h b/utest.h
index 26bf890..58c83c7 100644
--- a/utest.h
+++ b/utest.h
@@ -69,19 +69,20 @@
 #endif
 
 #if defined(_MSC_VER)
-#if defined(_M_IX86)
-#define _X86_
-#endif
+typedef union {
+  struct {
+    unsigned long LowPart;
+    long  HighPart;
+  } DUMMYSTRUCTNAME;
+  struct {
+    unsigned long LowPart;
+    long  HighPart;
+  } u;
+  utest_int64_t QuadPart;
+} utest_large_integer;
 
-#if defined(_M_AMD64)
-#define _AMD64_
-#endif
-
-#pragma warning(push, 1)
-#include <windef.h>
-#include <winbase.h>
-#pragma warning(pop)
-
+__declspec(dllimport) int __stdcall QueryPerformanceCounter(utest_large_integer *);
+__declspec(dllimport) int __stdcall QueryPerformanceFrequency(utest_large_integer *);
 #elif defined(__linux__)
 
 /*
@@ -194,8 +195,8 @@
 
 static UTEST_INLINE utest_int64_t utest_ns(void) {
 #ifdef _MSC_VER
-  LARGE_INTEGER counter;
-  LARGE_INTEGER frequency;
+  utest_large_integer counter;
+  utest_large_integer frequency;
   QueryPerformanceCounter(&counter);
   QueryPerformanceFrequency(&frequency);
   return UTEST_CAST(utest_int64_t,