diff --git a/iseq.c b/iseq.c
index 2f25e187bf..73423d9074 100644
--- a/iseq.c
+++ b/iseq.c
@@ -3130,7 +3130,7 @@ rb_vm_encoded_insn_data_table_init(void)
             traced_insn = BIN(opt_invokebuiltin_delegate); // to dispatch :return from leave
         }
         st_data_t key1 = (st_data_t)INSN_CODE(insn);
-        st_data_t key2 = (st_data_t)INSN_CODE(traced_insn + VM_INSTRUCTION_SIZE/2);
+        st_data_t key2 = (st_data_t)INSN_CODE((st_data_t)traced_insn + VM_INSTRUCTION_SIZE/2);
 
         insn_data[insn].insn = (int)insn;
         insn_data[insn].insn_len = insn_len(insn);