2 files changed, 3 insertions, 3 deletions

diff --git a/src/lib_os.c b/src/lib_os.c
index d6ca70f69..7821fc1fd 100644
--- a/src/lib_os.c
+++ b/src/lib_os.c
@@ -240,8 +240,8 @@ LJLIB_CF(os_time)
     ts.tm_min = getfield(L, "min", 0);
     ts.tm_hour = getfield(L, "hour", 12);
     ts.tm_mday = getfield(L, "day", -1);
-    ts.tm_mon = getfield(L, "month", -1) - 1;
-    ts.tm_year = getfield(L, "year", -1) - 1900;
+    ts.tm_mon = (int)((unsigned int)getfield(L, "month", -1) - 1u);
+    ts.tm_year = (int)((unsigned int)getfield(L, "year", -1) - 1900u);
     ts.tm_isdst = getboolfield(L, "isdst");
     t = mktime(&ts);
   }
diff --git a/src/lj_carith.c b/src/lj_carith.c
index 12c3ced28..cb408fb80 100644
--- a/src/lj_carith.c
+++ b/src/lj_carith.c
@@ -135,7 +135,7 @@ static int carith_ptr(lua_State *L, CTState *cts, CDArith *ca, MMS mm)
       return 0;
     lj_cconv_ct_ct(cts, ctype_get(cts, CTID_INT_PSZ), ca->ct[1],
                    (uint8_t *)&idx, ca->p[1], 0);
-    if (mm == MM_sub) idx = -idx;
+    if (mm == MM_sub) idx = (ptrdiff_t)(~(uintptr_t)idx+1u);
   } else if (mm == MM_add && ctype_isnum(ctp->info) &&
       (ctype_isptr(ca->ct[1]->info) || ctype_isrefarray(ca->ct[1]->info))) {
     /* Swap pointer and index. */