diff --git a/src/lj_strfmt_num.c b/src/lj_strfmt_num.c
index 79bc7610..04769258 100644
--- a/src/lj_strfmt_num.c
+++ b/src/lj_strfmt_num.c
@@ -480,7 +480,7 @@ static char *lj_strfmt_wfnum(SBuf *sb, SFormat sf, lua_Number n, char *p)
       if ((prec | (sf & STRFMT_F_ALT))) {
 	/* Emit fractional part. */
 	p[1] = '.'; p += 2;
-	prec -= (q - p); p = q; /* Account for the digits already emitted. */
+	prec -= (MSize)(q - p); p = q; /* Account for digits already emitted. */
 	/* Then emit chunks of 9 digits (this may emit 8 digits too many). */
 	for (i = ndhi; (int32_t)prec > 0 && i != ndlo; prec -= 9) {
 	  i = (i - 1) & 0x3f;
diff --git a/src/vm_x64.dasc b/src/vm_x64.dasc
index a6b6853e..63ed2cb7 100644
--- a/src/vm_x64.dasc
+++ b/src/vm_x64.dasc
@@ -250,11 +250,11 @@
 |// Macros to clear or set tags.
 |.macro cleartp, reg; shl reg, 17; shr reg, 17; .endmacro
 |.macro settp, reg, tp
-|  mov64 ITYPE, ((int64_t)tp<<47)
+|  mov64 ITYPE, ((uint64_t)tp<<47)
 |  or reg, ITYPE
 |.endmacro
 |.macro settp, dst, reg, tp
-|  mov64 dst, ((int64_t)tp<<47)
+|  mov64 dst, ((uint64_t)tp<<47)
 |  or dst, reg
 |.endmacro
 |.macro setint, reg