diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index ce0bfad64f7b069b7bf7e3f8a8cd12d01ac5833e..a2bd7017ee14ffe3bd1af62296da0f7c40219d4f 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,5 +1,9 @@
 2013-02-05  Jason Merrill  <jason@redhat.com>
 
+	PR c++/56177
+	* decl.c (start_preparsed_function): Update restype if we change
+	decl1.
+
 	PR c++/56208
 	* pt.c (fn_type_unification): Discard any access checks from
 	substituting explicit args.
diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index 9b40018370fd5b2190782c9e16876379b6ffbf60..cfee0f8d37dab7949b09d49f3e91cbaf59ed8ca3 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -13116,6 +13116,7 @@ start_preparsed_function (tree decl1, tree attrs, int flags)
 	    DECL_CONTEXT (decl1) = DECL_CONTEXT (DECL_TI_TEMPLATE (decl1));
 	}
       fntype = TREE_TYPE (decl1);
+      restype = TREE_TYPE (fntype);
 
       /* If #pragma weak applies, mark the decl appropriately now.
 	 The pragma only applies to global functions.  Because
diff --git a/gcc/testsuite/g++.dg/cpp1y/auto-fn14.C b/gcc/testsuite/g++.dg/cpp1y/auto-fn14.C
new file mode 100644
index 0000000000000000000000000000000000000000..e7e86991ed3aa30f9e17dcce8083c9a47fead4c7
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1y/auto-fn14.C
@@ -0,0 +1,5 @@
+// PR c++/56177
+// { dg-options "-std=c++1y" }
+
+auto f ();
+auto f () { return 33; }