diff --git a/src/lj_strscan.c b/src/lj_strscan.c
index 1b4e72f6..7efde2fd 100644
--- a/src/lj_strscan.c
+++ b/src/lj_strscan.c
@@ -552,7 +552,7 @@ int LJ_FASTCALL lj_strscan_number(GCstr *str, TValue *o)
 }
 #endif
 
-static int strscan_base(GCstr *str, TValue *o, int base, int dualnum)
+static int32_t strscan_base(GCstr *str, TValue *o, int32_t base, int dualnum)
 {
   const char *p = strdata(str);
   char *ep;
@@ -561,7 +561,7 @@ static int strscan_base(GCstr *str, TValue *o, int base, int dualnum)
   while (lj_char_isspace((unsigned char)(*p))) p++;
   if (*p == '-') { p++; neg = 1; } else if (*p == '+') { p++; }
   if (lj_char_isalnum((unsigned char)(*p))) {
-    ul = strtoul(p, &ep, base);
+    ul = strtoul(p, &ep, (int)base);
     if (p != ep) {
       while (lj_char_isspace((unsigned char)(*ep))) ep++;
       if (*ep == '\0') {
@@ -580,13 +580,13 @@ static int strscan_base(GCstr *str, TValue *o, int base, int dualnum)
   return 0;
 }
 
-LJ_FUNC int lj_strscan_num_base(GCstr *str, TValue *o, int base)
+LJ_FUNC int32_t lj_strscan_num_base(GCstr *str, TValue *o, int32_t base)
 {
   return strscan_base(str, o, base, 0);
 }
 
 #if LJ_DUALNUM
-LJ_FUNC int lj_strscan_number_base(GCstr *str, TValue *o, int base)
+LJ_FUNC int32_t lj_strscan_number_base(GCstr *str, TValue *o, int32_t base)
 {
   return strscan_base(str, o, base, 1);
 }
diff --git a/src/lj_strscan.h b/src/lj_strscan.h
index 9c915ee1..8caadd1d 100644
--- a/src/lj_strscan.h
+++ b/src/lj_strscan.h
@@ -38,9 +38,9 @@ static LJ_AINLINE int lj_strscan_numberobj(TValue *o)
 }
 
 /* The base must be between 2 and 36. */
-LJ_FUNC int lj_strscan_num_base(GCstr *str, TValue *o, int base);
+LJ_FUNC int32_t lj_strscan_num_base(GCstr *str, TValue *o, int32_t base);
 #if LJ_DUALNUM
-LJ_FUNC int lj_strscan_number_base(GCstr *str, TValue *o, int base);
+LJ_FUNC int32_t lj_strscan_number_base(GCstr *str, TValue *o, int32_t base);
 #else
 #define lj_strscan_number_base(s, o, base) \
   lj_strscan_num_base((s), (o), (base))