diff --git a/libc/src/__support/UInt.h b/libc/src/__support/UInt.h
index c49c8314cd495..d92d61ed094eb 100644
--- a/libc/src/__support/UInt.h
+++ b/libc/src/__support/UInt.h
@@ -14,10 +14,10 @@
 #include "src/__support/CPP/limits.h"
 #include "src/__support/CPP/optional.h"
 #include "src/__support/CPP/type_traits.h"
-#include "src/__support/macros/attributes.h"       // LIBC_INLINE
-#include "src/__support/macros/optimization.h"     // LIBC_UNLIKELY
-#include "src/__support/macros/properties/types.h" // LIBC_TYPES_HAS_INT128
-#include "src/__support/math_extras.h"             // SumCarry, DiffBorrow
+#include "src/__support/macros/attributes.h"   // LIBC_INLINE
+#include "src/__support/macros/optimization.h" // LIBC_UNLIKELY
+#include "src/__support/macros/properties/types.h" // LIBC_TYPES_HAS_INT128, LIBC_TYPES_HAS_INT64
+#include "src/__support/math_extras.h" // SumCarry, DiffBorrow
 #include "src/__support/number_pair.h"
 
 #include <stddef.h> // For size_t
@@ -940,11 +940,11 @@ namespace internal {
 // availability.
 template <size_t Bits>
 struct WordTypeSelector : cpp::type_identity<
-#if defined(UINT64_MAX)
+#ifdef LIBC_TYPES_HAS_INT64
                               uint64_t
 #else
                               uint32_t
-#endif
+#endif // LIBC_TYPES_HAS_INT64
                               > {
 };
 // Except if we request 32 bits explicitly.
diff --git a/libc/src/__support/macros/properties/types.h b/libc/src/__support/macros/properties/types.h
index 42345e4743cef..d43cf99e6859b 100644
--- a/libc/src/__support/macros/properties/types.h
+++ b/libc/src/__support/macros/properties/types.h
@@ -17,7 +17,7 @@
 #include "src/__support/macros/properties/cpu_features.h"
 #include "src/__support/macros/properties/os.h"
 
-#include <stdint.h> // __SIZEOF_INT128__
+#include <stdint.h> // UINT64_MAX, __SIZEOF_INT128__
 
 // 'long double' properties.
 #if (LDBL_MANT_DIG == 53)
@@ -28,6 +28,11 @@
 #define LIBC_TYPES_LONG_DOUBLE_IS_FLOAT128
 #endif
 
+// int64 / uint64 support
+#if defined(UINT64_MAX)
+#define LIBC_TYPES_HAS_INT64
+#endif // UINT64_MAX
+
 // int128 / uint128 support
 #if defined(__SIZEOF_INT128__)
 #define LIBC_TYPES_HAS_INT128
diff --git a/libc/src/string/memory_utils/op_generic.h b/libc/src/string/memory_utils/op_generic.h
index 41fc1fa0f1ff0..efaff80b7e4da 100644
--- a/libc/src/string/memory_utils/op_generic.h
+++ b/libc/src/string/memory_utils/op_generic.h
@@ -28,6 +28,7 @@
 #include "src/__support/common.h"
 #include "src/__support/endian.h"
 #include "src/__support/macros/optimization.h"
+#include "src/__support/macros/properties/types.h" // LIBC_TYPES_HAS_INT64
 #include "src/string/memory_utils/op_builtin.h"
 #include "src/string/memory_utils/utils.h"
 
@@ -37,10 +38,6 @@ static_assert((UINTPTR_MAX == 4294967295U) ||
                   (UINTPTR_MAX == 18446744073709551615UL),
               "We currently only support 32- or 64-bit platforms");
 
-#if defined(UINT64_MAX)
-#define LLVM_LIBC_HAS_UINT64
-#endif
-
 namespace LIBC_NAMESPACE {
 // Compiler types using the vector attributes.
 using generic_v128 = uint8_t __attribute__((__vector_size__(16)));
@@ -60,9 +57,9 @@ template <typename T> struct is_scalar : cpp::false_type {};
 template <> struct is_scalar<uint8_t> : cpp::true_type {};
 template <> struct is_scalar<uint16_t> : cpp::true_type {};
 template <> struct is_scalar<uint32_t> : cpp::true_type {};
-#ifdef LLVM_LIBC_HAS_UINT64
+#ifdef LIBC_TYPES_HAS_INT64
 template <> struct is_scalar<uint64_t> : cpp::true_type {};
-#endif // LLVM_LIBC_HAS_UINT64
+#endif // LIBC_TYPES_HAS_INT64
 // Meant to match std::numeric_limits interface.
 // NOLINTNEXTLINE(readability-identifier-naming)
 template <typename T> constexpr bool is_scalar_v = is_scalar<T>::value;
diff --git a/libc/test/src/string/memory_utils/op_tests.cpp b/libc/test/src/string/memory_utils/op_tests.cpp
index 15ac9607bf3e3..95a04755eb4db 100644
--- a/libc/test/src/string/memory_utils/op_tests.cpp
+++ b/libc/test/src/string/memory_utils/op_tests.cpp
@@ -7,9 +7,9 @@
 //===----------------------------------------------------------------------===//
 
 #include "memory_check_utils.h"
+#include "src/__support/macros/properties/types.h" // LIBC_TYPES_HAS_INT64
 #include "src/string/memory_utils/op_aarch64.h"
 #include "src/string/memory_utils/op_builtin.h"
-#include "src/string/memory_utils/op_generic.h" // LLVM_LIBC_HAS_UINT64
 #include "src/string/memory_utils/op_riscv.h"
 #include "src/string/memory_utils/op_x86.h"
 #include "test/UnitTest/Test.h"
@@ -124,9 +124,9 @@ using MemsetImplementations = testing::TypeList<
     builtin::Memset<32>, //
     builtin::Memset<64>,
 #endif
-#ifdef LLVM_LIBC_HAS_UINT64
+#ifdef LIBC_TYPES_HAS_INT64
     generic::Memset<uint64_t>, generic::Memset<cpp::array<uint64_t, 2>>,
-#endif
+#endif // LIBC_TYPES_HAS_INT64
 #ifdef __AVX512F__
     generic::Memset<generic_v512>, generic::Memset<cpp::array<generic_v512, 2>>,
 #endif
@@ -210,9 +210,9 @@ using BcmpImplementations = testing::TypeList<
 #ifndef LIBC_TARGET_ARCH_IS_ARM // Removing non uint8_t types for ARM
     generic::Bcmp<uint16_t>,
     generic::Bcmp<uint32_t>, //
-#ifdef LLVM_LIBC_HAS_UINT64
+#ifdef LIBC_TYPES_HAS_INT64
     generic::Bcmp<uint64_t>,
-#endif // LLVM_LIBC_HAS_UINT64
+#endif // LIBC_TYPES_HAS_INT64
     generic::BcmpSequence<uint16_t, uint8_t>,
     generic::BcmpSequence<uint32_t, uint8_t>,  //
     generic::BcmpSequence<uint32_t, uint16_t>, //
@@ -292,9 +292,9 @@ using MemcmpImplementations = testing::TypeList<
 #ifndef LIBC_TARGET_ARCH_IS_ARM // Removing non uint8_t types for ARM
     generic::Memcmp<uint16_t>,
     generic::Memcmp<uint32_t>, //
-#ifdef LLVM_LIBC_HAS_UINT64
+#ifdef LIBC_TYPES_HAS_INT64
     generic::Memcmp<uint64_t>,
-#endif // LLVM_LIBC_HAS_UINT64
+#endif // LIBC_TYPES_HAS_INT64
     generic::MemcmpSequence<uint16_t, uint8_t>,
     generic::MemcmpSequence<uint32_t, uint16_t, uint8_t>, //
 #endif // LIBC_TARGET_ARCH_IS_ARM