diff --git a/include/boost/unordered/detail/hash_table.hpp b/include/boost/unordered/detail/hash_table.hpp
index 26a0455a..2a7431ff 100644
--- a/include/boost/unordered/detail/hash_table.hpp
+++ b/include/boost/unordered/detail/hash_table.hpp
@@ -83,7 +83,7 @@ namespace boost {
             1610612741ul, 3221225473ul, 4294967291ul };
 
         template<typename T>
-        std::ptrdiff_t const prime_list_template<T>::length = 28;
+        std::ptrdiff_t const prime_list_template<T>::length = 40;
 
         typedef prime_list_template<std::size_t> prime_list;
 
diff --git a/test/unordered/Jamfile.v2 b/test/unordered/Jamfile.v2
index 9ecec284..a524fa31 100644
--- a/test/unordered/Jamfile.v2
+++ b/test/unordered/Jamfile.v2
@@ -37,4 +37,5 @@ test-suite unordered
         [ run rehash_tests.cpp ]
         [ run equality_tests.cpp ]
         [ run swap_tests.cpp : : : <define>BOOST_UNORDERED_SWAP_METHOD=2 ]
+        [ run detail_tests.cpp ]
     ;
diff --git a/test/unordered/detail_tests.cpp b/test/unordered/detail_tests.cpp
new file mode 100644
index 00000000..daa89895
--- /dev/null
+++ b/test/unordered/detail_tests.cpp
@@ -0,0 +1,27 @@
+
+// Copyright 2009 Daniel James.
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+// Test some of the library's implementation details.
+
+#include <boost/unordered_set.hpp>
+#include <boost/unordered_map.hpp>
+
+#include <boost/detail/lightweight_test.hpp>
+#include <boost/range.hpp>
+
+int main() {
+    
+    // Test that the prime list has the right length.
+    // 
+    // It would have been better to automatically set the length in the header
+    // but that doesn't work on some older compilers.
+
+    BOOST_TEST_EQ(
+        boost::end(boost::unordered_detail::prime_list::value) -
+        boost::begin(boost::unordered_detail::prime_list::value),
+        boost::unordered_detail::prime_list::length);
+
+    return boost::report_errors();
+}
\ No newline at end of file