diff --git a/.github/workflows/wide_integer_fuzzing.yml b/.github/workflows/wide_integer_fuzzing.yml
index 7ab258f..ff2be9d 100644
--- a/.github/workflows/wide_integer_fuzzing.yml
+++ b/.github/workflows/wide_integer_fuzzing.yml
@@ -46,4 +46,4 @@ jobs:
           clang++ -std=c++20 -g -O2 -fsanitize=fuzzer -I. -I../boost-root test/fuzzing/test_fuzzing_${{ matrix.tcase }}.cpp -o test_fuzzing_${{ matrix.tcase }}
           echo "ls test_fuzzing_${{ matrix.tcase }}"
           ls -la test_fuzzing_${{ matrix.tcase }}
-          ./test_fuzzing_${{ matrix.tcase }} -max_total_time=240 -jobs=8
+          ./test_fuzzing_${{ matrix.tcase }} -max_total_time=300 -jobs=8
diff --git a/test/fuzzing/test_fuzzing_prime.cpp b/test/fuzzing/test_fuzzing_prime.cpp
index fd3ff36..898ce75 100644
--- a/test/fuzzing/test_fuzzing_prime.cpp
+++ b/test/fuzzing/test_fuzzing_prime.cpp
@@ -15,13 +15,10 @@
 #include <boost/multiprecision/cpp_int.hpp>
 #include <boost/multiprecision/miller_rabin.hpp>
 
-#include <algorithm>
 #include <cassert>
 #include <cstddef>
 #include <cstdint>
 #include <random>
-#include <sstream>
-#include <vector>
 
 namespace fuzzing
 {
@@ -65,32 +62,30 @@ auto fuzzing::eval_prime(const std::uint8_t* data, std::size_t size) -> bool
     distribution_type distribution2;
 
     local_uint_type p0 { 0U };
+    boost_uint_type pb { 0U };
 
     // Import the random data into the prime candidate.
     import_bits
     (
       p0,
       data,
-      data + size
+      data + size,
+      8U
     );
 
-    const bool miller_rabin_result_local { miller_rabin(p0, 25U, distribution2, generator2) };
-
-    auto from_string =
-      [](const local_uint_type& ui)
-      {
-        std::stringstream strm { };
-
-        strm << ui;
-
-        return boost_uint_type { strm.str() };
-      };
-
-    const boost_uint_type pb { std::move(from_string(p0)) };
+    // Import the random data into the boost control prime candidate.
+    import_bits
+    (
+      pb,
+      data,
+      data + size,
+      8U
+    );
 
     // Ensure that both uintwide_t as well as boost obtain
     // the same prime (or non-prime) result.
 
+    const bool miller_rabin_result_local { miller_rabin(p0, 25U, distribution2, generator2) };
     const bool miller_rabin_result_boost { boost::multiprecision::miller_rabin_test(pb, 25U, generator2) };
 
     const bool
diff --git a/test/test_uintwide_t_spot_values.cpp b/test/test_uintwide_t_spot_values.cpp
index 477d2a3..3b35719 100644
--- a/test/test_uintwide_t_spot_values.cpp
+++ b/test/test_uintwide_t_spot_values.cpp
@@ -5,13 +5,94 @@
 //  or copy at http://www.boost.org/LICENSE_1_0.txt)
 //
 
+#include <test/test_uintwide_t.h>
+#include <math/wide_integer/uintwide_t.h>
+
+#include <boost/multiprecision/cpp_int.hpp>
+
 #include <algorithm>
 #include <array>
 #include <cassert>
 #include <sstream>
+#include <string>
+#include <vector>
 
-#include <math/wide_integer/uintwide_t.h>
-#include <test/test_uintwide_t.h>
+namespace from_issue_429
+{
+  auto test_uintwide_t_spot_values_from_issue_429() -> bool
+  {
+    #if defined(WIDE_INTEGER_NAMESPACE)
+    using local_uint_type = WIDE_INTEGER_NAMESPACE::math::wide_integer::uint256_t;
+    #else
+    using local_uint_type = ::math::wide_integer::uint256_t;
+    #endif
+
+    using boost_uint_backend_type =
+      boost::multiprecision::cpp_int_backend<static_cast<unsigned>(UINT32_C(256)),
+                                             static_cast<unsigned>(UINT32_C(256)),
+                                             boost::multiprecision::unsigned_magnitude>;
+
+    using boost_uint_type = boost::multiprecision::number<boost_uint_backend_type,
+                                                          boost::multiprecision::et_off>;
+
+
+    const std::vector<std::uint8_t>
+      input
+      (
+        {
+          0x00, 0x00, 0x00, 0xff,
+          0xff, 0xff, 0xff, 0xff,
+          0xff, 0xff, 0x21, 0x62,
+          0xff, 0xff, 0xff, 0xff,
+          0x21
+        }
+    );
+
+    local_uint_type p0_local { };
+    boost_uint_type p0_boost { };
+
+    // Import the data into the wide integer.
+    import_bits
+    (
+      p0_local,
+      input.cbegin(),
+      input.cend(),
+      8U
+    );
+
+    // Import the data into boost's cpp_int.
+    import_bits
+    (
+      p0_boost,
+      input.cbegin(),
+      input.cend(),
+      8U
+    );
+
+    std::stringstream strm_local { };
+    std::stringstream strm_boost { };
+
+    strm_local << std::hex << p0_local;
+    strm_boost << std::hex << p0_boost;
+
+    const std::string str_local { strm_local.str() };
+    const std::string str_boost { strm_boost.str() };
+
+    const bool result_import_is_ok { str_local == str_boost };
+
+    std::vector<std::uint8_t> export_local(input.size());
+    std::vector<std::uint8_t> export_boost(input.size());
+
+    export_bits(p0_local, export_local.begin(), 8U);
+    export_bits(p0_boost, export_boost.begin(), 8U);
+
+    const bool result_export_is_ok { export_local == export_boost };
+
+    const bool result_import_export_is_ok { result_import_is_ok && result_export_is_ok };
+
+    return result_import_export_is_ok;
+  }
+} // namespace from_issue_429
 
 namespace from_issue_362
 {
@@ -651,6 +732,12 @@ auto local_test_spot_values::test() -> bool // NOLINT(readability-function-cogni
 {
   auto result_is_ok = true;
 
+  {
+    // See also: https://github.com/ckormanyos/wide-integer/issues/429
+
+    result_is_ok = (from_issue_429::test_uintwide_t_spot_values_from_issue_429() && result_is_ok);
+  }
+
   {
     // See also: https://github.com/ckormanyos/wide-integer/issues/362