diff --git a/asm/assembler/constpool.c b/asm/assembler/constpool.c
index 30c7136..de20b2d 100644
--- a/asm/assembler/constpool.c
+++ b/asm/assembler/constpool.c
@@ -93,6 +93,7 @@ static ivy_extended_data_key write_selector(
 
 	size_t i = 0;
 	size_t nr_args = b_queue_length(&sel->sel_args);
+	dat.sel_nr_args = (uint8_t)nr_args;
 	/* TODO hash. */
 
 	ivy_extended_data_key *arg_handles