diff --git a/src/pl/plperl/plperl.c b/src/pl/plperl/plperl.c
index 840df2e..6a1d2bb 100644
--- a/src/pl/plperl/plperl.c
+++ b/src/pl/plperl/plperl.c
@@ -2100,8 +2100,11 @@ plperl_call_perl_func(plperl_proc_desc *desc, FunctionCallInfo fcinfo)
 	PUSHMARK(SP);
 	EXTEND(sp, desc->nargs);
 
-	if (fcinfo->flinfo->fn_oid)
+	if (OidIsValid(fcinfo->flinfo->fn_oid))
+	{
 		get_func_signature(fcinfo->flinfo->fn_oid, &argtypes, &nargs);
+		Assert(nargs == desc->nargs);
+	}
 
 	for (i = 0; i < desc->nargs; i++)
 	{
@@ -2120,7 +2123,8 @@ plperl_call_perl_func(plperl_proc_desc *desc, FunctionCallInfo fcinfo)
 
 			if (OidIsValid(desc->arg_arraytype[i]))
 				sv = plperl_ref_from_pg_array(fcinfo->arg[i], desc->arg_arraytype[i]);
-			else if ((funcid = get_transform_fromsql(argtypes[i], current_call_data->prodesc->lang_oid, current_call_data->prodesc->trftypes)))
+			else if (OidIsValid(fcinfo->flinfo->fn_oid) &&
+				(funcid = get_transform_fromsql(argtypes[i], current_call_data->prodesc->lang_oid, current_call_data->prodesc->trftypes)))
 				sv = (SV *) DatumGetPointer(OidFunctionCall1(funcid, fcinfo->arg[i]));
 			else
 			{