diff --git a/gcc/fortran/ChangeLog b/gcc/fortran/ChangeLog
index 9bd81c388b8..a15c13663ef 100644
--- a/gcc/fortran/ChangeLog
+++ b/gcc/fortran/ChangeLog
@@ -1,3 +1,10 @@
+2010-08-27  Janus Weil  <janus@gcc.gnu.org>
+
+	PR fortran/45420
+	* match.c (select_type_set_tmp): Add the possibility to reset the
+	temporary to NULL.
+	(gfc_match_class_is): Reset the temporary in CLASS DEFAULT clauses.
+
 2010-08-27  Thomas Koenig  <tkoenig@gcc.gnu.org>
 
 	PR fortran/45159
diff --git a/gcc/fortran/match.c b/gcc/fortran/match.c
index 21dbcde8b7b..7c0dfc7478d 100644
--- a/gcc/fortran/match.c
+++ b/gcc/fortran/match.c
@@ -4460,6 +4460,12 @@ select_type_set_tmp (gfc_typespec *ts)
   char name[GFC_MAX_SYMBOL_LEN];
   gfc_symtree *tmp;
   
+  if (!ts)
+    {
+      select_type_stack->tmp = NULL;
+      return;
+    }
+  
   if (!gfc_type_is_extensible (ts->u.derived))
     return;
 
@@ -4708,6 +4714,7 @@ gfc_match_class_is (void)
       c->where = gfc_current_locus;
       c->ts.type = BT_UNKNOWN;
       new_st.ext.case_list = c;
+      select_type_set_tmp (NULL);
       return MATCH_YES;
     }
 
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 734b2b7b213..bf917998c93 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2010-08-27  Janus Weil  <janus@gcc.gnu.org>
+
+	PR fortran/45420
+	* gfortran.dg/select_type_15.f03: New.
+
 2010-08-27  Jerry DeLisle  <jvdelisle@gcc.gnu.org>
 
 	PR libfortran/43217
diff --git a/gcc/testsuite/gfortran.dg/select_type_15.f03 b/gcc/testsuite/gfortran.dg/select_type_15.f03
new file mode 100644
index 00000000000..6be045c097e
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/select_type_15.f03
@@ -0,0 +1,77 @@
+! { dg-do run }
+!
+! PR 45420: [OOP] polymorphic TBP call in a CLASS DEFAULT clause
+!
+! Contributed by Salvatore Filippone <salvatore.filippone@uniroma2.it>
+
+
+module base_mat_mod
+
+ type  :: base_sparse_mat
+ contains
+   procedure, pass(a) :: get_fmt => base_get_fmt
+ end type base_sparse_mat
+
+contains
+
+ function base_get_fmt(a) result(res)
+   implicit none
+   class(base_sparse_mat), intent(in) :: a
+   character(len=5) :: res
+   res = 'NULL'
+ end function base_get_fmt
+
+end module base_mat_mod
+
+
+module d_base_mat_mod
+
+ use base_mat_mod
+
+ type, extends(base_sparse_mat) :: d_base_sparse_mat
+ contains
+   procedure, pass(a) :: get_fmt => d_base_get_fmt
+ end type d_base_sparse_mat
+
+ type, extends(d_base_sparse_mat) :: x_base_sparse_mat
+ contains
+   procedure, pass(a) :: get_fmt => x_base_get_fmt
+ end type x_base_sparse_mat
+
+contains
+
+ function d_base_get_fmt(a) result(res)
+   implicit none
+   class(d_base_sparse_mat), intent(in) :: a
+   character(len=5) :: res
+   res = 'DBASE'
+ end function d_base_get_fmt
+
+ function x_base_get_fmt(a) result(res)
+   implicit none
+   class(x_base_sparse_mat), intent(in) :: a
+   character(len=5) :: res
+   res = 'XBASE'
+ end function x_base_get_fmt
+
+end module d_base_mat_mod
+
+
+program bug20
+  use d_base_mat_mod
+  class(d_base_sparse_mat), allocatable  :: a
+
+  allocate(x_base_sparse_mat :: a)
+  if (a%get_fmt()/="XBASE") call abort()
+
+  select type(a)
+  type is (d_base_sparse_mat)
+    call abort()
+  class default
+    if (a%get_fmt()/="XBASE") call abort()
+  end select
+
+end program bug20
+
+
+! { dg-final { cleanup-modules "base_mat_mod d_base_mat_mod" } }