diff --git a/src/core/os.c b/src/core/os.c
index 251d5ff2..da0a3340 100644
--- a/src/core/os.c
+++ b/src/core/os.c
@@ -309,7 +309,7 @@ static EnvBlock os_execute_env(int32_t argc, const Janet *argv) {
     JanetDictView dict = janet_getdictionary(argv, 2);
 #ifdef JANET_WINDOWS
     JanetBuffer *temp = janet_buffer(10);
-    for (int32_t i = 0; i < dict.cap; i++) {
+    for (size_t i = 0; i < dict.cap; i++) {
         const JanetKV *kv = dict.kvs + i;
         if (!janet_checktype(kv->key, JANET_STRING)) continue;
         if (!janet_checktype(kv->value, JANET_STRING)) continue;
@@ -380,7 +380,7 @@ static void os_execute_cleanup(EnvBlock envp, const char **child_argv) {
  * a single string of this format. Returns a buffer that can be cast into a c string. */
 static JanetBuffer *os_exec_escape(JanetView args) {
     JanetBuffer *b = janet_buffer(0);
-    for (int32_t i = 0; i < args.len; i++) {
+    for (size_t i = 0; i < args.len; i++) {
         const char *arg = janet_getcstring(args.items, i);
 
         /* Push leading space if not first */
diff --git a/src/core/pp.c b/src/core/pp.c
index 94d78fa7..569d49da 100644
--- a/src/core/pp.c
+++ b/src/core/pp.c
@@ -895,13 +895,13 @@ void janet_formatbv(JanetBuffer *b, const char *format, va_list args) {
                 case 's':
                 case 'S': {
                     const char *str = va_arg(args, const char *);
-                    int32_t len = c[-1] == 's'
-                                  ? (int32_t) strlen(str)
+                    size_t len = c[-1] == 's'
+                                  ? strlen(str)
                                   : janet_string_length((JanetString) str);
                     if (form[2] == '\0')
                         janet_buffer_push_bytes(b, (const uint8_t *) str, len);
                     else {
-                        if (len != (int32_t) strlen((const char *) str))
+                        if (len != strlen((const char *) str))
                             janet_panic("string contains zeros");
                         if (!strchr(form, '.') && len >= 100) {
                             janet_panic("no precision and string is too long to be formatted");