diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index c89020ef029..24fc5ae6486 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,9 @@
+2017-01-24  Jonathan Wakely  <jwakely@redhat.com>
+
+	PR libstdc++/79206
+	* include/experimental/string_view (operator==): Check sizes first.
+	* include/std/string_view (operator==): Likewise.
+
 2017-01-23  Jonathan Wakely  <jwakely@redhat.com>
 
 	* testsuite/experimental/array/make_array.cc: Restore <functional>
diff --git a/libstdc++-v3/include/experimental/string_view b/libstdc++-v3/include/experimental/string_view
index eaff0cc764c..2a2364cfa1e 100644
--- a/libstdc++-v3/include/experimental/string_view
+++ b/libstdc++-v3/include/experimental/string_view
@@ -456,19 +456,19 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     inline bool
     operator==(basic_string_view<_CharT, _Traits> __x,
                basic_string_view<_CharT, _Traits> __y) noexcept
-    { return __x.compare(__y) == 0; }
+    { return __x.size() == __y.size() && __x.compare(__y) == 0; }
 
   template<typename _CharT, typename _Traits>
     inline bool
     operator==(basic_string_view<_CharT, _Traits> __x,
                __detail::__idt<basic_string_view<_CharT, _Traits>> __y) noexcept
-    { return __x.compare(__y) == 0; }
+    { return __x.size() == __y.size() && __x.compare(__y) == 0; }
 
   template<typename _CharT, typename _Traits>
     inline bool
     operator==(__detail::__idt<basic_string_view<_CharT, _Traits>> __x,
                basic_string_view<_CharT, _Traits> __y) noexcept
-    { return __x.compare(__y) == 0; }
+    { return __x.size() == __y.size() && __x.compare(__y) == 0; }
 
   template<typename _CharT, typename _Traits>
     inline bool
diff --git a/libstdc++-v3/include/std/string_view b/libstdc++-v3/include/std/string_view
index 9eee528102c..a71918553bb 100644
--- a/libstdc++-v3/include/std/string_view
+++ b/libstdc++-v3/include/std/string_view
@@ -453,19 +453,19 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     inline bool
     operator==(basic_string_view<_CharT, _Traits> __x,
                basic_string_view<_CharT, _Traits> __y) noexcept
-    { return __x.compare(__y) == 0; }
+    { return __x.size() == __y.size() && __x.compare(__y) == 0; }
 
   template<typename _CharT, typename _Traits>
     inline bool
     operator==(basic_string_view<_CharT, _Traits> __x,
                __detail::__idt<basic_string_view<_CharT, _Traits>> __y) noexcept
-    { return __x.compare(__y) == 0; }
+    { return __x.size() == __y.size() && __x.compare(__y) == 0; }
 
   template<typename _CharT, typename _Traits>
     inline bool
     operator==(__detail::__idt<basic_string_view<_CharT, _Traits>> __x,
                basic_string_view<_CharT, _Traits> __y) noexcept
-    { return __x.compare(__y) == 0; }
+    { return __x.size() == __y.size() && __x.compare(__y) == 0; }
 
   template<typename _CharT, typename _Traits>
     inline bool