1 files changed, 1 insertions, 1 deletions

diff --git a/src/lib_base.c b/src/lib_base.c
index 8c1e98a6..eb604538 100644
--- a/src/lib_base.c
+++ b/src/lib_base.c
@@ -301,7 +301,7 @@ LJLIB_ASM(tonumber)		LJLIB_REC(.)
         while (lj_char_isspace((unsigned char)(*ep))) ep++;
         if (*ep == '\0') {
           if (LJ_DUALNUM && LJ_LIKELY(ul < 0x80000000u+neg)) {
-            if (neg) ul = -ul;
+            if (neg) ul = (unsigned long)-(long)ul;
             setintV(L->base-1-LJ_FR2, (int32_t)ul);
           } else {
             lua_Number n = (lua_Number)ul;