diff --git a/performance/performance_test.cpp b/performance/performance_test.cpp
@@ -294,25 +294,25 @@ struct tester
    }
    double test_left_shift()
    {
-      int shift = std::numeric_limits<T>::is_bounded ? std::numeric_limits<T>::digits : bits_wanted;
-      shift /= 2;
+      int max_shift = std::numeric_limits<T>::is_bounded ? std::numeric_limits<T>::digits : bits_wanted;
+      int shift = 0;
       stopwatch<boost::chrono::high_resolution_clock> w;
       for(unsigned i = 0; i < 1000; ++i)
       {
          for(unsigned i = 0; i < b.size(); ++i)
-            a[i] = b[i] << shift;
+            a[i] = b[i] << (shift++ % max_shift);
       }
       return boost::chrono::duration_cast<boost::chrono::duration<double> >(w.elapsed()).count();
    }
    double test_right_shift()
    {
-      int shift = std::numeric_limits<T>::is_bounded ? std::numeric_limits<T>::digits : bits_wanted;
-      shift /= 2;
+      int max_shift = 2 + std::numeric_limits<T>::is_bounded ? std::numeric_limits<T>::digits : bits_wanted;
+      int shift  = 0;
       stopwatch<boost::chrono::high_resolution_clock> w;
       for(unsigned i = 0; i < 1000; ++i)
       {
          for(unsigned i = 0; i < b.size(); ++i)
-            a[i] = b[i] >> shift;
+            a[i] = b[i] >> (shift++) % max_shift;
       }
       return boost::chrono::duration_cast<boost::chrono::duration<double> >(w.elapsed()).count();
    }

diff --git a/test/test_cpp_int.cpp b/test/test_cpp_int.cpp
@@ -11,6 +11,12 @@
 #  define _SCL_SECURE_NO_WARNINGS
 #endif
 
+//
+// This ensures all our code gets tested, even though it may
+// not be the fastest configuration in normal use:
+//
+#define BOOST_MP_USE_LIMB_SHIFT
+
 #include <boost/multiprecision/gmp.hpp>
 #include <boost/multiprecision/cpp_int.hpp>
 #include <boost/random/mersenne_twister.hpp>