diff --git a/libstdc++-v3/include/ext/random b/libstdc++-v3/include/ext/random
index 41a2962c8f6e5..d5574e02ba02c 100644
--- a/libstdc++-v3/include/ext/random
+++ b/libstdc++-v3/include/ext/random
@@ -752,6 +752,21 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 				_InputIterator2 __varbegin,
 				_InputIterator2 __varend);
 
+	// param_type constructors apply Cholesky decomposition to the
+	// varcov matrix in _M_init_full and _M_init_lower, but the
+	// varcov matrix output ot a stream is already decomposed, so
+	// we need means to restore it as-is when reading it back in.
+	template<size_t _Dimen1, typename _RealType1,
+		 typename _CharT, typename _Traits>
+	friend std::basic_istream<_CharT, _Traits>&
+	operator>>(std::basic_istream<_CharT, _Traits>& __is,
+		   __gnu_cxx::normal_mv_distribution<_Dimen1, _RealType1>&
+		   __x);
+	param_type(std::array<_RealType, _Dimen> const &__mean,
+		   std::array<_RealType, _M_t_size> const &__varcov)
+	  : _M_mean (__mean), _M_t (__varcov)
+	{}
+
 	std::array<_RealType, _Dimen> _M_mean;
 	std::array<_RealType, _M_t_size> _M_t;
       };
diff --git a/libstdc++-v3/include/ext/random.tcc b/libstdc++-v3/include/ext/random.tcc
index 31dc33a2555ed..a8a49a3a9fa6a 100644
--- a/libstdc++-v3/include/ext/random.tcc
+++ b/libstdc++-v3/include/ext/random.tcc
@@ -581,7 +581,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	    __sum = *__varcovbegin++ - __sum;
 	    if (__builtin_expect(__sum <= _RealType(0), 0))
 	      std::__throw_runtime_error(__N("normal_mv_distribution::"
-					     "param_type::_M_init_full"));
+					     "param_type::_M_init_lower"));
 	    *__w++ = std::sqrt(__sum);
 	  }
       }
@@ -709,9 +709,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
       __is >> __x._M_nd;
 
+      // The param_type temporary is built with a private constructor,
+      // to skip the Cholesky decomposition that would be performed
+      // otherwise.
       __x.param(typename normal_mv_distribution<_Dimen, _RealType>::
-		param_type(__mean.begin(), __mean.end(),
-			   __varcov.begin(), __varcov.end()));
+		param_type(__mean, __varcov));
 
       __is.flags(__flags);
       return __is;
diff --git a/libstdc++-v3/testsuite/ext/random/beta_distribution/operators/serialize.cc b/libstdc++-v3/testsuite/ext/random/beta_distribution/operators/serialize.cc
index b05417156d191..a4925fc1c41be 100644
--- a/libstdc++-v3/testsuite/ext/random/beta_distribution/operators/serialize.cc
+++ b/libstdc++-v3/testsuite/ext/random/beta_distribution/operators/serialize.cc
@@ -23,6 +23,7 @@
 
 #include <ext/random>
 #include <sstream>
+#include <testsuite_hooks.h>
 
 void
 test01()
@@ -35,6 +36,7 @@ test01()
   str << u;
 
   str >> v;
+  VERIFY( u == v );
 }
 
 int main()
diff --git a/libstdc++-v3/testsuite/ext/random/hypergeometric_distribution/operators/serialize.cc b/libstdc++-v3/testsuite/ext/random/hypergeometric_distribution/operators/serialize.cc
index 9c2cc46ac1ce0..e9077b2c58d65 100644
--- a/libstdc++-v3/testsuite/ext/random/hypergeometric_distribution/operators/serialize.cc
+++ b/libstdc++-v3/testsuite/ext/random/hypergeometric_distribution/operators/serialize.cc
@@ -38,6 +38,7 @@ test01()
   str << u;
 
   str >> v;
+  VERIFY( u == v );
 }
 
 int
diff --git a/libstdc++-v3/testsuite/ext/random/normal_mv_distribution/operators/serialize.cc b/libstdc++-v3/testsuite/ext/random/normal_mv_distribution/operators/serialize.cc
index 8d83f9e6966d2..f5fbc42a686f0 100644
--- a/libstdc++-v3/testsuite/ext/random/normal_mv_distribution/operators/serialize.cc
+++ b/libstdc++-v3/testsuite/ext/random/normal_mv_distribution/operators/serialize.cc
@@ -23,6 +23,7 @@
 
 #include <ext/random>
 #include <sstream>
+#include <testsuite_hooks.h>
 
 void
 test01()
@@ -35,6 +36,7 @@ test01()
   str << u;
 
   str >> v;
+  VERIFY( u == v );
 }
 
 int main()
diff --git a/libstdc++-v3/testsuite/ext/random/triangular_distribution/operators/serialize.cc b/libstdc++-v3/testsuite/ext/random/triangular_distribution/operators/serialize.cc
index cf17fea8b03ff..75e16cf0437cb 100644
--- a/libstdc++-v3/testsuite/ext/random/triangular_distribution/operators/serialize.cc
+++ b/libstdc++-v3/testsuite/ext/random/triangular_distribution/operators/serialize.cc
@@ -23,6 +23,7 @@
 
 #include <ext/random>
 #include <sstream>
+#include <testsuite_hooks.h>
 
 void
 test01()
@@ -35,6 +36,7 @@ test01()
   str << u;
 
   str >> v;
+  VERIFY( u == v );
 }
 
 int main()
diff --git a/libstdc++-v3/testsuite/ext/random/von_mises_distribution/operators/serialize.cc b/libstdc++-v3/testsuite/ext/random/von_mises_distribution/operators/serialize.cc
index f3d7912e314ba..b32a31dee6421 100644
--- a/libstdc++-v3/testsuite/ext/random/von_mises_distribution/operators/serialize.cc
+++ b/libstdc++-v3/testsuite/ext/random/von_mises_distribution/operators/serialize.cc
@@ -23,6 +23,7 @@
 
 #include <ext/random>
 #include <sstream>
+#include <testsuite_hooks.h>
 
 void
 test01()
@@ -35,6 +36,7 @@ test01()
   str << u;
 
   str >> v;
+  VERIFY( u == v );
 }
 
 int main()
