diff --git a/plugins/ets/runtime/intrinsics/std_math.cpp b/plugins/ets/runtime/intrinsics/std_math.cpp
index 9fcb6540e2be6cc0497776653f73adf54a14668a..a817c33ab5ef0fad33e857d6b7980a74497aa28f 100644
--- a/plugins/ets/runtime/intrinsics/std_math.cpp
+++ b/plugins/ets/runtime/intrinsics/std_math.cpp
@@ -20,9 +20,6 @@
 
 namespace panda::ets::intrinsics {
 
-constexpr const uint32_t BIT_32 = 0x80000000;
-constexpr const uint64_t BIT_64 = 0x8000000000000000;
-
 extern "C" double StdMathRandom()
 {
     std::random_device rd;
@@ -98,32 +95,12 @@ extern "C" double StdMathCeil(double val)
 
 extern "C" int32_t StdMathClz64(int64_t val)
 {
-    uint64_t bit = BIT_64;
-    int32_t count = 0;
-    while (bit >= 1) {
-        if ((static_cast<uint64_t>(val) & bit) == 0) {
-            bit /= 2;
-            count++;
-        } else {
-            break;
-        }
-    }
-    return count;
+    return std::__countl_zero(static_cast<uint64_t>(val));
 }
 
 extern "C" int32_t StdMathClz32(int32_t val)
 {
-    uint32_t bit = BIT_32;
-    int32_t count = 0;
-    while (bit >= 1) {
-        if ((static_cast<uint32_t>(val) & bit) == 0) {
-            bit /= 2;
-            count++;
-        } else {
-            break;
-        }
-    }
-    return count;
+    return std::__countl_zero(static_cast<uint32_t>(val));
 }
 
 extern "C" double StdMathLog(double val)
diff --git a/plugins/ets/tests/ets-templates/06.conversions_and_contexts/Test.ets b/plugins/ets/tests/ets-templates/06.conversions_and_contexts/Test.ets
new file mode 100644
index 0000000000000000000000000000000000000000..7a7941e62333e979ffa967faaf45f813ec6eca9e
--- /dev/null
+++ b/plugins/ets/tests/ets-templates/06.conversions_and_contexts/Test.ets
@@ -0,0 +1,14 @@
+// function main(): void {
+//     console.println("--------");
+//     let i: long = 0x00000000ffffffff;
+//     let j: int = 0xffffffff;
+//     if (clz64(i) == clz32(j)) {
+//         console.println("NOT HEHE")
+//     }
+//     console.println(clz32(j))
+//     console.print(clz64(i))
+//     console.println(" ----- instead of 32...");
+// }
+function main(): void {
+    console.println(clz64(0x00000000ffffffffL))
+}
\ No newline at end of file