diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index be05727fd9e..e364bec617f 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,9 @@
+2011-01-24  Johannes Singler  <singler@kit.edu>
+
+        PR libstdc++/47437
+        * include/parallel/multiway_merge.h (_UnguardedIterator):
+        Remove useless "mutable" from reference declaration.
+
 2011-01-21  Benjamin Kosnik  <bkoz@redhat.com>
 
 	* include/bits/c++config (_GLIBCXX_EXPORT_TEMPLATE): Remove.
diff --git a/libstdc++-v3/include/parallel/multiway_merge.h b/libstdc++-v3/include/parallel/multiway_merge.h
index 1baf76beb9c..0fd3da2d656 100644
--- a/libstdc++-v3/include/parallel/multiway_merge.h
+++ b/libstdc++-v3/include/parallel/multiway_merge.h
@@ -143,7 +143,7 @@ namespace __gnu_parallel
       /** @brief Current iterator __position. */
       _RAIter _M_current;
       /** @brief _Compare. */
-      mutable _Compare& __comp;
+      _Compare& __comp;
 
     public:
       /** @brief Constructor. Sets iterator to beginning of sequence.