diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index f62d01c60..860818a03 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -356,12 +356,13 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
+        arch: [x64, Win32]
         buildType: [Debug, Release]
     steps:
       - uses: actions/checkout@v4
       - name: build
         run: |
-          cmake -B build -G "Visual Studio 17 2022"
+          cmake -B build -G "Visual Studio 17 2022" -A ${{matrix.arch}}
           cmake --build build --config ${{matrix.buildType}} --target qjs_exe
           cmake --build build --config ${{matrix.buildType}} --target function_source
       - name: stats
diff --git a/cutils.h b/cutils.h
index a5da60db7..26436d4f2 100644
--- a/cutils.h
+++ b/cutils.h
@@ -203,9 +203,16 @@ static inline int clz32(unsigned int a)
 static inline int clz64(uint64_t a)
 {
 #if defined(_MSC_VER) && !defined(__clang__)
+#if INTPTR_MAX == INT64_MAX
     unsigned long index;
     _BitScanReverse64(&index, a);
     return 63 - index;
+#else
+    if (a >> 32)
+        return clz32((unsigned)(a >> 32));
+    else
+        return clz32((unsigned)a) + 32;
+#endif	
 #else
     return __builtin_clzll(a);
 #endif
diff --git a/tests/test_conv.c b/tests/test_conv.c
index 9761b30d0..b0678ae5c 100644
--- a/tests/test_conv.c
+++ b/tests/test_conv.c
@@ -94,14 +94,20 @@ static inline int clz32(unsigned int a)
 static inline int clz64(uint64_t a)
 {
 #if defined(_MSC_VER) && !defined(__clang__)
+#if INTPTR_MAX == INT64_MAX
     unsigned long index;
     _BitScanReverse64(&index, a);
     return 63 - index;
+#else
+    if (a >> 32)
+        return clz32((unsigned)(a >> 32));
+    else
+        return clz32((unsigned)a) + 32;
+#endif	
 #else
     return __builtin_clzll(a);
 #endif
 }
-
 // prototypes for final functions
 extern char const digits36[36];
 size_t u32toa(char buf[minimum_length(11)], uint32_t n);