diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index cbc497836d1..873c59b30a6 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,12 @@
+2002-07-02  Paolo Carlini  <pcarlini@unitus.it>
+
+	PR libstdc++/6642
+	* include/bits/stl_iterator.h
+	(__normal_iterator::operator-(const __normal_iterator&)):
+	Make non-member, as already happens for the comparison
+	operators in accord with DR179 (Ready).
+	* testsuite/24_iterators/iterator.cc: Add test from the PR.
+
 2002-07-02  Phil Edwards  <pme@gcc.gnu.org>
 
 	PR libstdc++/7173
diff --git a/libstdc++-v3/include/bits/stl_iterator.h b/libstdc++-v3/include/bits/stl_iterator.h
index d8a6d8ca374..6fb0d81339f 100644
--- a/libstdc++-v3/include/bits/stl_iterator.h
+++ b/libstdc++-v3/include/bits/stl_iterator.h
@@ -629,10 +629,6 @@ namespace __gnu_cxx
       operator-(const difference_type& __n) const
       { return __normal_iterator(_M_current - __n); }
       
-      difference_type
-      operator-(const __normal_iterator& __i) const
-      { return _M_current - __i._M_current; }
-      
       const _Iterator& 
       base() const { return _M_current; }
     };
@@ -719,6 +715,16 @@ namespace __gnu_cxx
 	     const __normal_iterator<_Iterator, _Container>& __rhs)
   { return __lhs.base() >= __rhs.base(); }
 
+  // _GLIBCPP_RESOLVE_LIB_DEFECTS
+  // According to the resolution of DR179 not only the various comparison
+  // operators but also operator- must accept mixed iterator/const_iterator
+  // parameters.
+  template<typename _IteratorL, typename _IteratorR, typename _Container>
+  inline typename __normal_iterator<_IteratorL, _Container>::difference_type
+  operator-(const __normal_iterator<_IteratorL, _Container>& __lhs,
+	     const __normal_iterator<_IteratorR, _Container>& __rhs)
+  { return __lhs.base() - __rhs.base(); }
+
   template<typename _Iterator, typename _Container>
   inline __normal_iterator<_Iterator, _Container>
   operator+(typename __normal_iterator<_Iterator, _Container>::difference_type __n,
diff --git a/libstdc++-v3/testsuite/24_iterators/iterator.cc b/libstdc++-v3/testsuite/24_iterators/iterator.cc
index 98aa8c0b258..7acd1ec26e1 100644
--- a/libstdc++-v3/testsuite/24_iterators/iterator.cc
+++ b/libstdc++-v3/testsuite/24_iterators/iterator.cc
@@ -577,6 +577,17 @@ wrong_stuff()
    return failures;
 }
 
+// libstdc++/6642
+int
+test6642()
+{
+   std::string s;
+   std::string::iterator it = s.begin();
+   std::string::const_iterator cit = s.begin();
+
+   return it - cit;
+}
+
 int
 main(int argc, char **argv)
 {
@@ -590,6 +601,8 @@ main(int argc, char **argv)
 
    failures += wrong_stuff();
 
+   failures += test6642();
+
 #ifdef DEBUG_ASSERT
    assert (failures == 0);
 #endif