diff --git a/moo/lib/exec.c b/moo/lib/exec.c
index c59faad..343f6d1 100644
--- a/moo/lib/exec.c
+++ b/moo/lib/exec.c
@@ -2174,11 +2174,14 @@ static moo_pfrc_t pf_context_find_exception_handler (moo_t* moo, moo_mod_t* mod,
 {
 	moo_oop_context_t rcv;
 	moo_ooi_t preamble;
-	moo_oop_t except_class;
+	moo_oop_class_t except_class;
 
 	rcv = (moo_oop_context_t)MOO_STACK_GETRCV(moo, nargs);
 	MOO_PF_CHECK_RCV (moo, MOO_CLASSOF(moo,rcv) == moo->_method_context);
 
+	except_class = MOO_STACK_GETARG(moo, nargs, 0);
+	MOO_PF_CHECK_ARGS (moo, nargs, MOO_CLASSOF(moo,rcv) == moo->_class);
+
 	preamble = MOO_OOP_TO_SMOOI(((moo_oop_method_t)rcv->method_or_nargs)->preamble);
 	if (MOO_METHOD_GET_PREAMBLE_CODE(preamble) == MOO_METHOD_PREAMBLE_EXCEPTION)
 	{
@@ -2186,8 +2189,6 @@ static moo_pfrc_t pf_context_find_exception_handler (moo_t* moo, moo_mod_t* mod,
 		 * on: ... do: ...*/
 		moo_oow_t size, i;
 
-		except_class = MOO_STACK_GETARG(moo, nargs, 0);
-
 		size = MOO_OBJ_GET_SIZE(rcv);
 		for (i = MOO_CONTEXT_NAMED_INSTVARS; i < size; i += 2)
 		{