diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index aa28747c8569..051faf6e6225 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,9 @@
+2009-07-07  Jason Merrill  <jason@redhat.com>
+
+	PR c++/35828
+	* pt.c (tsubst_decl): Don't abort if we didn't change anything
+	in a TEMPLATE_DECL's args.
+
 2009-07-07  Manuel López-Ibáñez  <manu@gcc.gnu.org>
 
 	* semantics.c (finalize_nrv_r): Replace EXPR_LOCUS by
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 2fc2223703c0..b4bd465860e2 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -8306,8 +8306,7 @@ tsubst_decl (tree t, tree args, tsubst_flags_t complain)
     case TEMPLATE_DECL:
       {
 	/* We can get here when processing a member function template,
-	   member class template, and template template parameter of
-	   a template class.  */
+	   member class template, or template template parameter.  */
 	tree decl = DECL_TEMPLATE_RESULT (t);
 	tree spec;
 	tree tmpl_args;
@@ -8351,10 +8350,10 @@ tsubst_decl (tree t, tree args, tsubst_flags_t complain)
 	if (full_args == error_mark_node)
 	  return error_mark_node;
 
-	/* tsubst_template_args doesn't copy the vector if
-	   nothing changed.  But, *something* should have
-	   changed.  */
-	gcc_assert (full_args != tmpl_args);
+	/* If this is a default template template argument,
+	   tsubst might not have changed anything.  */
+	if (full_args == tmpl_args)
+	  return t;
 
 	hash = hash_tmpl_and_args (t, full_args);
 	spec = retrieve_specialization (t, full_args, hash);
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 9e4ec3defb15..3f35f440fd93 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,5 +1,8 @@
 2009-07-07  Jason Merrill  <jason@redhat.com>
 
+	PR c++/35828
+	* g++.dg/template/defarg12.C: New.
+
 	PR c++/37816
 	* g++.dg/cpp0x/enum7.C: New.
 
diff --git a/gcc/testsuite/g++.dg/template/defarg12.C b/gcc/testsuite/g++.dg/template/defarg12.C
new file mode 100644
index 000000000000..d11848af2286
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/defarg12.C
@@ -0,0 +1,10 @@
+// PR c++/35828
+// { dg-options "-std=c++0x" }
+
+template < typename > struct A ;
+template < template < typename > class = A >
+void test ()
+{
+        test ();
+}
+