diff --git a/src/core/buffer.c b/src/core/buffer.c
index 3a56d5b92..dfe1859ff 100644
--- a/src/core/buffer.c
+++ b/src/core/buffer.c
@@ -314,7 +314,7 @@ JANET_CORE_FN(cfun_buffer_chars,
     return argv[0];
 }
 
-static int should_reverse_bytes(const Janet *argv, size_t argc) {
+static int should_reverse_bytes(const Janet *argv, int32_t argc) {
     JanetKeyword order_kw = janet_getkeyword(argv, argc);
     if (!janet_cstrcmp(order_kw, "le")) {
 #if JANET_BIG_ENDIAN
diff --git a/src/core/capi.c b/src/core/capi.c
index b4e8fa921..d4cb74046 100644
--- a/src/core/capi.c
+++ b/src/core/capi.c
@@ -353,7 +353,7 @@ size_t janet_gethalfrange(const Janet *argv, int32_t n, size_t length, const cha
     ssize_t not_raw = raw;
     if (not_raw < 0) not_raw += length + 1;
     if (not_raw < 0 || (size_t) not_raw > length)
-        janet_panicf("%s index %d out of range [%o,%o]", which, (int64_t) raw, -(uint64_t)length - 1, (uint64_t) length);
+        janet_panicf("%s index %d out of range [%d,%d]", which, (int64_t) raw, -(int64_t)length - 1, (int64_t) length);
     return (size_t) not_raw;
 }
 
@@ -376,7 +376,7 @@ size_t janet_getargindex(const Janet *argv, int32_t n, size_t length, const char
     ssize_t not_raw = raw;
     if (not_raw < 0) not_raw += length;
     if (not_raw < 0 || (size_t) not_raw > length)
-        janet_panicf("%s index %d out of range [%o,%o)", which, (int64_t)raw, -(uint64_t)length, (uint64_t)length);
+        janet_panicf("%s index %d out of range [%d,%d)", which, (int64_t)raw, -(int64_t)length, (int64_t)length);
     return (size_t) not_raw;
 }
 
@@ -457,13 +457,13 @@ void janet_setdyn(const char *name, Janet value) {
 uint64_t janet_getflags(const Janet *argv, int32_t n, const char *flags) {
     uint64_t ret = 0;
     const uint8_t *keyw = janet_getkeyword(argv, n);
-    int32_t klen = janet_string_length(keyw);
-    int32_t flen = (int32_t) strlen(flags);
+    size_t klen = janet_string_length(keyw);
+    size_t flen = strlen(flags);
     if (flen > 64) {
         flen = 64;
     }
-    for (int32_t j = 0; j < klen; j++) {
-        for (int32_t i = 0; i < flen; i++) {
+    for (size_t j = 0; j < klen; j++) {
+        for (size_t i = 0; i < flen; i++) {
             if (((uint8_t) flags[i]) == keyw[j]) {
                 ret |= 1ULL << i;
                 goto found;
diff --git a/src/core/compile.c b/src/core/compile.c
index 2d9a3ebba..8d6613cb3 100644
--- a/src/core/compile.c
+++ b/src/core/compile.c
@@ -418,12 +418,11 @@ JanetSlot janetc_gettarget(JanetFopts opts) {
 }
 
 /* Get a bunch of slots for function arguments */
-JanetSlot *janetc_toslots(JanetCompiler *c, const Janet *vals, int32_t len) {
-    int32_t i;
+JanetSlot *janetc_toslots(JanetCompiler *c, const Janet *vals, size_t len) {
     JanetSlot *ret = NULL;
     JanetFopts subopts = janetc_fopts_default(c);
     subopts.flags |= JANET_FOPTS_ACCEPT_SPLICE;
-    for (i = 0; i < len; i++) {
+    for (size_t i = 0; i < len; i++) {
         janet_v_push(ret, janetc_value(subopts, vals[i]));
     }
     return ret;
diff --git a/src/core/compile.h b/src/core/compile.h
index 05e6f39b7..e372fb9f4 100644
--- a/src/core/compile.h
+++ b/src/core/compile.h
@@ -232,7 +232,7 @@ void janetc_throwaway(JanetFopts opts, Janet x);
 JanetSlot janetc_gettarget(JanetFopts opts);
 
 /* Get a bunch of slots for function arguments */
-JanetSlot *janetc_toslots(JanetCompiler *c, const Janet *vals, int32_t len);
+JanetSlot *janetc_toslots(JanetCompiler *c, const Janet *vals, size_t len);
 
 /* Get a bunch of slots for function arguments */
 JanetSlot *janetc_toslotskv(JanetCompiler *c, Janet ds);
diff --git a/src/core/debug.c b/src/core/debug.c
index 35b2b3316..0a3215e38 100644
--- a/src/core/debug.c
+++ b/src/core/debug.c
@@ -120,7 +120,7 @@ void janet_stacktrace_ext(JanetFiber *fiber, Janet err, const char *prefix) {
 
     for (fi = janet_v_count(fibers) - 1; fi >= 0; fi--) {
         fiber = fibers[fi];
-        int32_t i = fiber->frame;
+        size_t i = fiber->frame;
         while (i > 0) {
             JanetCFunRegistry *reg = NULL;
             JanetStackFrame *frame = (JanetStackFrame *)(fiber->data + i - JANET_FRAME_SIZE);
@@ -374,7 +374,7 @@ JANET_CORE_FN(cfun_debug_stack,
     JanetFiber *fiber = janet_getfiber(argv, 0);
     JanetArray *array = janet_array(0);
     {
-        int32_t i = fiber->frame;
+        size_t i = fiber->frame;
         JanetStackFrame *frame;
         while (i > 0) {
             frame = (JanetStackFrame *)(fiber->data + i - JANET_FRAME_SIZE);
diff --git a/src/core/ev.c b/src/core/ev.c
index f20da22f1..9e43c2324 100644
--- a/src/core/ev.c
+++ b/src/core/ev.c
@@ -1246,9 +1246,9 @@ static void janet_chanat_marshal(void *p, JanetMarshalContext *ctx) {
     janet_marshal_byte(ctx, channel->is_threaded);
     janet_marshal_abstract(ctx, channel);
     janet_marshal_byte(ctx, channel->closed);
-    janet_marshal_int(ctx, channel->limit);
-    int32_t count = janet_q_count(&channel->items);
-    janet_marshal_int(ctx, count);
+    janet_marshal_size(ctx, channel->limit);
+    size_t count = janet_q_count(&channel->items);
+    janet_marshal_size(ctx, count);
     JanetQueue *items = &channel->items;
     Janet *data = channel->items.data;
     if (items->head <= items->tail) {
@@ -2475,7 +2475,7 @@ void ev_callback_write(JanetFiber *fiber, JanetAsyncEvent event) {
         break;
         case JANET_ASYNC_EVENT_INIT: {
             /* Begin write */
-            int32_t len;
+            size_t len;
             const uint8_t *bytes;
             if (state->is_buffer) {
                 /* If buffer, convert to string. */
diff --git a/src/core/fiber.c b/src/core/fiber.c
index 33a945eb3..5660ce091 100644
--- a/src/core/fiber.c
+++ b/src/core/fiber.c
@@ -288,10 +288,10 @@ int janet_env_valid(JanetFuncEnv *env) {
     if (env->offset < 0) {
         int32_t real_offset = -(env->offset);
         JanetFiber *fiber = env->as.fiber;
-        int32_t i = fiber->frame;
+        size_t i = fiber->frame;
         while (i > 0) {
             JanetStackFrame *frame = (JanetStackFrame *)(fiber->data + i - JANET_FRAME_SIZE);
-            if (real_offset == i &&
+            if ((size_t) real_offset == i &&
                     frame->env == env &&
                     frame->func &&
                     frame->func->def->slotcount == env->length) {
diff --git a/src/core/gc.c b/src/core/gc.c
index 462a5b49b..1145d576b 100644
--- a/src/core/gc.c
+++ b/src/core/gc.c
@@ -122,7 +122,7 @@ static void janet_mark_abstract(void *adata) {
 }
 
 /* Mark a bunch of items in memory */
-static void janet_mark_many(const Janet *values, int32_t n) {
+static void janet_mark_many(const Janet *values, size_t n) {
     if (values == NULL)
         return;
     const Janet *end = values + n;
@@ -262,7 +262,7 @@ static void janet_mark_function(JanetFunction *func) {
 }
 
 static void janet_mark_fiber(JanetFiber *fiber) {
-    int32_t i, j;
+    size_t i, j;
     JanetStackFrame *frame;
 recur:
     if (janet_gc_reachable(fiber))
diff --git a/src/core/io.c b/src/core/io.c
index 20825d088..8eda892bb 100644
--- a/src/core/io.c
+++ b/src/core/io.c
@@ -59,8 +59,7 @@ const JanetAbstractType janet_file_type = {
 /* Check arguments to fopen */
 static int32_t checkflags(const uint8_t *str) {
     int32_t flags = 0;
-    int32_t i;
-    int32_t len = janet_string_length(str);
+    size_t len = janet_string_length(str);
     if (!len || len > 10)
         janet_panic("file mode must have a length between 1 and 10");
     switch (*str) {
@@ -80,7 +79,7 @@ static int32_t checkflags(const uint8_t *str) {
             janet_sandbox_assert(JANET_SANDBOX_FS_READ);
             break;
     }
-    for (i = 1; i < len; i++) {
+    for (size_t i = 1; i < len; i++) {
         switch (str[i]) {
             default:
                 janet_panicf("invalid flag %c, expected +, b, or n", str[i]);
@@ -489,7 +488,7 @@ static Janet cfun_io_print_impl_x(int32_t argc, Janet *argv, int newline,
         }
     }
     for (int32_t i = offset; i < argc; ++i) {
-        int32_t len;
+        size_t len;
         const uint8_t *vstr;
         if (janet_checktype(argv[i], JANET_BUFFER)) {
             JanetBuffer *b = janet_unwrap_buffer(argv[i]);
diff --git a/src/core/os.c b/src/core/os.c
index 1fedd8ce5..0715d1839 100644
--- a/src/core/os.c
+++ b/src/core/os.c
@@ -1670,9 +1670,8 @@ JANET_CORE_FN(os_cryptorand,
               "Get or append `n` bytes of good quality random data provided by the OS. Returns a new buffer or `buf`.") {
     JanetBuffer *buffer;
     janet_arity(argc, 1, 2);
-    int32_t offset;
-    int32_t n = janet_getinteger(argv, 0);
-    if (n < 0) janet_panic("expected positive integer");
+    size_t offset;
+    size_t n = janet_getsize(argv, 0);
     if (argc == 2) {
         buffer = janet_getbuffer(argv, 1);
         offset = buffer->count;
diff --git a/src/core/parse.c b/src/core/parse.c
index 6821f51bd..2c6eea9e5 100644
--- a/src/core/parse.c
+++ b/src/core/parse.c
@@ -434,8 +434,8 @@ static int stringchar(JanetParser *p, JanetParseState *state, uint8_t c) {
 }
 
 /* Check for string equality in the buffer */
-static int check_str_const(const char *cstr, const uint8_t *str, int32_t len) {
-    int32_t index;
+static int check_str_const(const char *cstr, const uint8_t *str, size_t len) {
+    size_t index;
     for (index = 0; index < len; index++) {
         uint8_t c = str[index];
         uint8_t k = ((const uint8_t *)cstr)[index];
@@ -974,7 +974,7 @@ JANET_CORE_FN(cfun_parse_insert,
         }
     } else if (s->flags & (PFLAG_STRING | PFLAG_LONGSTRING)) {
         const uint8_t *str = janet_to_string(argv[1]);
-        int32_t slen = janet_string_length(str);
+        size_t slen = janet_string_length(str);
         size_t newcount = p->bufcount + slen;
         if (p->bufcap < newcount) {
             size_t newcap = 2 * newcount;
diff --git a/src/core/peg.c b/src/core/peg.c
index 72d2ddf9f..39fb82632 100644
--- a/src/core/peg.c
+++ b/src/core/peg.c
@@ -65,9 +65,9 @@ typedef struct {
  * to save state at branches, and then reload
  * if one branch fails and try a new branch. */
 typedef struct {
-    int32_t cap;
-    int32_t tcap;
-    int32_t scratch;
+    size_t cap;
+    size_t tcap;
+    size_t scratch;
 } CapState;
 
 /* Save the current capture state */
diff --git a/src/core/pp.c b/src/core/pp.c
index 569d49dac..9bfcb76b7 100644
--- a/src/core/pp.c
+++ b/src/core/pp.c
@@ -134,9 +134,9 @@ static void string_description_b(JanetBuffer *buffer, const char *title, void *p
 #undef POINTSIZE
 }
 
-static void janet_escape_string_impl(JanetBuffer *buffer, const uint8_t *str, int32_t len) {
+static void janet_escape_string_impl(JanetBuffer *buffer, const uint8_t *str, size_t len) {
     janet_buffer_push_u8(buffer, '"');
-    for (int32_t i = 0; i < len; ++i) {
+    for (size_t i = 0; i < len; ++i) {
         uint8_t c = str[i];
         switch (c) {
             case '"':
diff --git a/src/core/specials.c b/src/core/specials.c
index db343f716..bf2f75177 100644
--- a/src/core/specials.c
+++ b/src/core/specials.c
@@ -72,7 +72,7 @@ static JanetSlot quasiquote(JanetFopts opts, Janet x, int depth, int level) {
         default:
             return janetc_cslot(x);
         case JANET_TUPLE: {
-            int32_t i, len;
+            size_t i, len;
             const Janet *tup = janet_unwrap_tuple(x);
             len = janet_tuple_length(tup);
             if (len > 1 && janet_checktype(tup[0], JANET_SYMBOL)) {
diff --git a/src/core/string.c b/src/core/string.c
index 824da2f5f..a4badf8f4 100644
--- a/src/core/string.c
+++ b/src/core/string.c
@@ -58,8 +58,8 @@ const uint8_t *janet_string(const uint8_t *buf, size_t len) {
 
 /* Compare two strings */
 int janet_string_compare(const uint8_t *lhs, const uint8_t *rhs) {
-    int32_t xlen = janet_string_length(lhs);
-    int32_t ylen = janet_string_length(rhs);
+    size_t xlen = janet_string_length(lhs);
+    size_t ylen = janet_string_length(rhs);
     size_t len = xlen > ylen ? ylen : xlen;
     int res = memcmp(lhs, rhs, len);
     if (res) return res > 0 ? 1 : -1;
@@ -574,14 +574,14 @@ static int trim_help_checkset(JanetByteView set, uint8_t x) {
     return 0;
 }
 
-static int32_t trim_help_leftedge(JanetByteView str, JanetByteView set) {
+static size_t trim_help_leftedge(JanetByteView str, JanetByteView set) {
     for (size_t i = 0; i < str.len; i++)
         if (!trim_help_checkset(set, str.bytes[i]))
             return i;
     return str.len;
 }
 
-static int32_t trim_help_rightedge(JanetByteView str, JanetByteView set) {
+static size_t trim_help_rightedge(JanetByteView str, JanetByteView set) {
     for (size_t i = str.len - 1; i > 0; i--)
         if (!trim_help_checkset(set, str.bytes[i]))
             return i + 1;
@@ -605,8 +605,8 @@ JANET_CORE_FN(cfun_string_trim,
               "`set` is provided, consider only characters in `set` to be whitespace.") {
     JanetByteView str, set;
     trim_help_args(argc, argv, &str, &set);
-    int32_t left_edge = trim_help_leftedge(str, set);
-    int32_t right_edge = trim_help_rightedge(str, set);
+    size_t left_edge = trim_help_leftedge(str, set);
+    size_t right_edge = trim_help_rightedge(str, set);
     if (right_edge < left_edge)
         return janet_stringv(NULL, 0);
     return janet_stringv(str.bytes + left_edge, right_edge - left_edge);
diff --git a/src/core/symcache.c b/src/core/symcache.c
index 41ce036e7..43ce6cbd2 100644
--- a/src/core/symcache.c
+++ b/src/core/symcache.c
@@ -66,7 +66,7 @@ static const uint8_t JANET_SYMCACHE_DELETED[1] = {0};
  * where one would put it. */
 static const uint8_t **janet_symcache_findmem(
     const uint8_t *str,
-    int32_t len,
+    size_t len,
     int32_t hash,
     int *success) {
     uint32_t bounds[4];
@@ -116,10 +116,10 @@ static const uint8_t **janet_symcache_findmem(
     janet_symcache_findmem((str), janet_string_length(str), janet_string_hash(str), (success))
 
 /* Resize the cache. */
-static void janet_cache_resize(uint32_t newCapacity) {
-    uint32_t i, oldCapacity;
+static void janet_cache_resize(size_t newCapacity) {
+    size_t i, oldCapacity;
     const uint8_t **oldCache = janet_vm.cache;
-    const uint8_t **newCache = janet_calloc(1, (size_t) newCapacity * sizeof(const uint8_t *));
+    const uint8_t **newCache = janet_calloc(1, newCapacity * sizeof(const uint8_t *));
     if (newCache == NULL) {
         JANET_OUT_OF_MEMORY;
     }
diff --git a/src/core/util.c b/src/core/util.c
index df255cfa1..2d6a73251 100644
--- a/src/core/util.c
+++ b/src/core/util.c
@@ -690,7 +690,7 @@ static JanetByteView to_byte_view(Janet value) {
 JanetByteView janet_text_substitution(
     Janet *subst,
     const uint8_t *bytes,
-    uint32_t len,
+    size_t len,
     JanetArray *extra_argv) {
     int32_t extra_argc = extra_argv == NULL ? 0 : extra_argv->count;
     JanetType type = janet_type(*subst);
diff --git a/src/core/util.h b/src/core/util.h
index 3ac69a694..0a8cbf88b 100644
--- a/src/core/util.h
+++ b/src/core/util.h
@@ -96,7 +96,7 @@ JanetBinding janet_binding_from_entry(Janet entry);
 JanetByteView janet_text_substitution(
     Janet *subst,
     const uint8_t *bytes,
-    uint32_t len,
+    size_t len,
     JanetArray *extra_args);
 
 /* Registry functions */
diff --git a/src/include/janet.h b/src/include/janet.h
index bb50bdc46..d4729f5c8 100644
--- a/src/include/janet.h
+++ b/src/include/janet.h
@@ -975,7 +975,7 @@ struct JanetStackFrame {
     JanetFunction *func;
     uint32_t *pc;
     JanetFuncEnv *env;
-    int32_t prevframe;
+    size_t prevframe;
     int32_t flags;
 };