diff --git a/src/lj_opt_split.c b/src/lj_opt_split.c
index 81ded6c0..4652c737 100644
--- a/src/lj_opt_split.c
+++ b/src/lj_opt_split.c
@@ -596,7 +596,8 @@ static void split_ir(jit_State *J)
 	}
 #endif
 	else if (st == IRT_I64 || st == IRT_U64) {  /* 64/64 bit cast. */
-	  /* Drop cast, since assembler doesn't care. */
+	  /* Drop cast, since assembler doesn't care. But fwd both parts. */
+	  hi = hiref;
 	  goto fwdlo;
 	} else if ((ir->op2 & IRCONV_SEXT)) {  /* Sign-extend to 64 bit. */
 	  IRRef k31 = lj_ir_kint(J, 31);