diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 4f08ec3961751a9e1f09b0e048e3fe88ca46ff74..2408adbf0357c29cf121446693f460d914add023 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,5 +1,8 @@
 2010-11-08  Jason Merrill  <jason@redhat.com>
 
+	PR c++/46335
+	* tree.c (bot_manip): Check TREE_SIDE_EFFECTS as well.
+
 	Correct conversion/overflow behavior.
 	* cvt.c (ignore_overflows): Move here from typeck.c.
 	(ocp_convert): Use it.
diff --git a/gcc/cp/tree.c b/gcc/cp/tree.c
index 5440e10204e2b1340cc54b709d3d228541561efe..462e35f3b71411c052d8489ec08a9a4c9717f098 100644
--- a/gcc/cp/tree.c
+++ b/gcc/cp/tree.c
@@ -1763,11 +1763,10 @@ bot_manip (tree* tp, int* walk_subtrees, void* data)
   splay_tree target_remap = ((splay_tree) data);
   tree t = *tp;
 
-  if (!TYPE_P (t) && TREE_CONSTANT (t))
+  if (!TYPE_P (t) && TREE_CONSTANT (t) && !TREE_SIDE_EFFECTS (t))
     {
       /* There can't be any TARGET_EXPRs or their slot variables below
-	 this point.  We used to check !TREE_SIDE_EFFECTS, but then we
-	 failed to copy an ADDR_EXPR of the slot VAR_DECL.  */
+	 this point.  */
       *walk_subtrees = 0;
       return NULL_TREE;
     }
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index e94dceff04371723547f955fd4f3af2a2e9283bf..1211aa299ed64af7c544fffb83e8eadd81669a14 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2010-11-08  Jason Merrill  <jason@redhat.com>
+
+	* g++.dg/cpp0x/constexpr-defarg.C: New.
+
 2010-11-08  Xinliang David Li  <davidxl@google.com>
 
 	PR/46316
diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-defarg.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-defarg.C
new file mode 100644
index 0000000000000000000000000000000000000000..1413b24bd842ac3cadbdcbbfb21ee1313cde2975
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-defarg.C
@@ -0,0 +1,12 @@
+// PR c++/46335
+// { dg-options -std=c++0x }
+
+struct T { };
+struct A {
+    A(const T &tr =T()) {}
+};
+struct B {
+    A k;
+};
+B kk_;
+A fk_;