diff --git a/src/core/model/int64x64-128.h b/src/core/model/int64x64-128.h
index 0c2a068b3..3b0c89afe 100644
--- a/src/core/model/int64x64-128.h
+++ b/src/core/model/int64x64-128.h
@@ -58,22 +58,11 @@ class int64x64_t
     static const uint128_t HP128_MASK_HI_BIT = (((int128_t)1) << 127);
     /// Mask for fraction part.
     static const uint64_t HP_MASK_LO = 0xffffffffffffffffULL;
-    /**
-     * Floating point value of HP_MASK_LO + 1.
-     * We really want:
-     * \code
-     *   static const long double HP_MAX_64 = std:pow (2.0L, 64);
-     * \endcode
-     * but we can't call functions in const definitions.
-     *
-     * We could make this a static and initialize in int64x64-128.cc or
-     * int64x64.cc, but this requires handling static initialization order
-     * when most of the implementation is inline.  Instead, we resort to
-     * this define.
-     */
-#define HP_MAX_64 (std::pow(2.0L, 64))
 
   public:
+    /// Floating point value of HP_MASK_LO + 1.
+    static constexpr long double HP_MAX_64 = (static_cast<uint64_t>(1) << 63) * 2.0L;
+
     /**
      * Type tag for the underlying implementation.
      *
diff --git a/src/core/model/int64x64-cairo.h b/src/core/model/int64x64-cairo.h
index e90d4d120..c0769b79f 100644
--- a/src/core/model/int64x64-cairo.h
+++ b/src/core/model/int64x64-cairo.h
@@ -44,21 +44,11 @@ class int64x64_t
     static const uint64_t HPCAIRO_MASK_HI_BIT = (((uint64_t)1) << 63);
     /// Mask for fraction part
     static const uint64_t HP_MASK_LO = 0xffffffffffffffffULL;
-    /**
-     * Floating point value of HP_MASK_LO + 1
-     * We really want:
-     * \code
-     *   static const long double HP_MAX_64 = std:pow (2.0L, 64);
-     * \endcode
-     * but we can't call functions in const definitions,
-     * We could make this a static and initialize in int64x64-cairo.cc or
-     * int64x64.cc, but this requires handling static initialization order
-     * when most of the implementation is inline.  Instead, we resort to
-     * this define.
-     */
-#define HP_MAX_64 (std::pow(2.0L, 64))
 
   public:
+    /// Floating point value of HP_MASK_LO + 1
+    static constexpr long double HP_MAX_64 = (static_cast<uint64_t>(1) << 63) * 2.0L;
+
     /**
      * Type tag for the underlying implementation.
      *
diff --git a/src/core/model/int64x64-double.h b/src/core/model/int64x64-double.h
index b965003c1..2f78c65f3 100644
--- a/src/core/model/int64x64-double.h
+++ b/src/core/model/int64x64-double.h
@@ -43,21 +43,11 @@ class int64x64_t
 {
     /// Mask for fraction part
     static const uint64_t HP_MASK_LO = 0xffffffffffffffffULL;
-    /**
-     * Floating point value of HP_MASK_LO + 1
-     * We really want:
-     * \code
-     *   static const long double HP_MAX_64 = std:pow (2.0L, 64);
-     * \endcode
-     * but we can't call functions in const definitions,
-     * We could make this a static and initialize in int64x64-double.cc or
-     * int64x64.cc, but this requires handling static initialization order
-     * when most of the implementation is inline.  Instead, we resort to
-     * this define.
-     */
-#define HP_MAX_64 (std::pow(2.0L, 64))
 
   public:
+    /// Floating point value of HP_MASK_LO + 1
+    static constexpr long double HP_MAX_64 = (static_cast<uint64_t>(1) << 63) * 2.0L;
+
     /**
      * Type tag for the underlying implementation.
      *
diff --git a/src/core/test/int64x64-test-suite.cc b/src/core/test/int64x64-test-suite.cc
index 877a965e8..43118875c 100644
--- a/src/core/test/int64x64-test-suite.cc
+++ b/src/core/test/int64x64-test-suite.cc
@@ -182,7 +182,8 @@ Int64x64HiLoTestCase::DoRun()
     if (int64x64_t::implementation == int64x64_t::ld_impl)
     {
         // Darwin 12.5.0 (Mac 10.8.5) g++ 4.2.1
-        low = static_cast<uint64_t>(HP_MAX_64 * std::numeric_limits<long double>::epsilon());
+        low = static_cast<uint64_t>(int64x64_t::HP_MAX_64 *
+                                    std::numeric_limits<long double>::epsilon());
     }
 
     Check(0, 0);