diff --git a/include/boost/multiprecision/cpp_df_qf/cpp_df_qf_detail.hpp b/include/boost/multiprecision/cpp_df_qf/cpp_df_qf_detail.hpp
index 59c6f6c2..23742463 100644
--- a/include/boost/multiprecision/cpp_df_qf/cpp_df_qf_detail.hpp
+++ b/include/boost/multiprecision/cpp_df_qf/cpp_df_qf_detail.hpp
@@ -32,6 +32,23 @@
 
 namespace boost { namespace multiprecision { namespace backends { namespace cpp_df_qf_detail {
 
+template <typename UnsignedIntegralType,
+          typename FloatType>
+constexpr auto float_mask() noexcept -> UnsignedIntegralType
+{
+   using local_unsigned_integral_type = UnsignedIntegralType;
+   using local_float_type = FloatType;
+
+   static_assert(static_cast<int>(sizeof(UnsignedIntegralType) * 8u) > static_cast<int>(cpp_df_qf_detail::ccmath::numeric_limits<local_float_type>::digits),
+                 "Error: this function is intended for unsigned integral type wider than the float type.");
+
+   return
+   {
+        local_unsigned_integral_type { local_unsigned_integral_type { 1 } << static_cast<unsigned>(cpp_df_qf_detail::ccmath::numeric_limits<local_float_type>::digits) }
+      - local_unsigned_integral_type { 1 }
+   };
+}
+
 template <class FloatingPointTypeA, class FloatingPointTypeB>
 struct pair
 {
diff --git a/include/boost/multiprecision/cpp_double_fp.hpp b/include/boost/multiprecision/cpp_double_fp.hpp
index c56e5f85..d2c90348 100644
--- a/include/boost/multiprecision/cpp_double_fp.hpp
+++ b/include/boost/multiprecision/cpp_double_fp.hpp
@@ -277,67 +277,27 @@ class cpp_double_fp_backend
                                         &&  boost::multiprecision::detail::is_unsigned<UnsignedIntegralType>::value
                                         && (static_cast<int>(sizeof(UnsignedIntegralType) * 8u) > cpp_df_qf_detail::ccmath::numeric_limits<float_type>::digits))>::type const* = nullptr>
    constexpr cpp_double_fp_backend(UnsignedIntegralType u)
+      : data(static_cast<float_type>(u & cpp_df_qf_detail::float_mask<UnsignedIntegralType, float_type>()),
+             static_cast<float_type>(0.0F))
    {
       using local_unsigned_integral_type = UnsignedIntegralType;
 
-      constexpr local_unsigned_integral_type
-         limb_mask
-         {
-              local_unsigned_integral_type { local_unsigned_integral_type { 1 } << static_cast<unsigned>(cpp_df_qf_detail::ccmath::numeric_limits<float_type>::digits) }
-            - local_unsigned_integral_type { 1 }
-         };
-
-      if (u <= limb_mask)
+      if (u > cpp_df_qf_detail::float_mask<UnsignedIntegralType, float_type>())
       {
-         data =
-         {
-            static_cast<float_type>(u),
-            static_cast<float_type>(0.0F)
-         };
-      }
-      else
-      {
-         constexpr local_unsigned_integral_type
-            flt_mask
+         local_unsigned_integral_type
+            local_flt_mask
             {
-               static_cast<local_unsigned_integral_type>
-               (
-                  static_cast<local_unsigned_integral_type>
-                  (
-                     static_cast<local_unsigned_integral_type>(UINT8_C(1)) << static_cast<unsigned>(cpp_df_qf_detail::ccmath::numeric_limits<float_type>::digits)
-                  )
-                  - static_cast<local_unsigned_integral_type>(UINT8_C(1))
-               )
+               cpp_df_qf_detail::float_mask<local_unsigned_integral_type, float_type>()
             };
 
-         data.second = static_cast<float_type>(0.0F);
-         data.first  = static_cast<float_type>(u & flt_mask);
-
-         constexpr float_type
-            p2_factor_digits
-            (
-               cpp_df_qf_detail::ccmath::ldexp
-               (
-                  static_cast<float_type>(1.0F),
-                  cpp_df_qf_detail::ccmath::numeric_limits<float_type>::digits
-               )
-            );
-
-         float_type p2_factor(p2_factor_digits);
-
-         while (u > static_cast<local_unsigned_integral_type>(UINT8_C(0)))
+         for (int     index_mask_lsb =  cpp_df_qf_detail::ccmath::numeric_limits<float_type>::digits;
+                     (index_mask_lsb <  static_cast<int>(sizeof(local_unsigned_integral_type) * 8u))
+                  && (local_flt_mask != local_unsigned_integral_type { UINT8_C(0) });
+                      index_mask_lsb += cpp_df_qf_detail::ccmath::numeric_limits<float_type>::digits)
          {
-            u >>= static_cast<unsigned>(cpp_df_qf_detail::ccmath::numeric_limits<float_type>::digits);
+            local_flt_mask <<= static_cast<unsigned>(cpp_df_qf_detail::ccmath::numeric_limits<float_type>::digits);
 
-            const float_type
-               xhi
-               {
-                  static_cast<float_type>(static_cast<float_type>(u & flt_mask) * p2_factor)
-               };
-
-            add_unchecked_limb(xhi);
-
-            p2_factor *= p2_factor_digits;
+            add_unchecked_limb(static_cast<float_type>(u & local_flt_mask));
          }
       }
    }
diff --git a/test/test_round.cpp b/test/test_round.cpp
index cd941b1e..89a69d82 100644
--- a/test/test_round.cpp
+++ b/test/test_round.cpp
@@ -519,18 +519,12 @@ int main()
 #endif
 #ifdef TEST_CPP_DOUBLE_FLOAT
 
-   // When using very old GCC, categorically disable this test for cpp_double_fp_backend.
-   // Do not attempt, at the moment, to track down the compiler's "internal failure".
-
-   #if (defined(BOOST_GCC) && !defined(BOOST_CLANG) && (BOOST_GCC < 80000))
-   #else
    test<boost::multiprecision::cpp_double_float>();
    test<boost::multiprecision::cpp_double_double>();
    test<boost::multiprecision::cpp_double_long_double>();
    #if defined(BOOST_MP_CPP_DOUBLE_FP_HAS_FLOAT128)
    test<boost::multiprecision::cpp_double_float128>();
    #endif
-   #endif
 
 #endif