diff --git a/upb/hash/common.c b/upb/hash/common.c
index 1e32f36f8a..8bc9087369 100644
--- a/upb/hash/common.c
+++ b/upb/hash/common.c
@@ -776,7 +776,7 @@ bool upb_inttable_next(const upb_inttable* t, uintptr_t* key, upb_value* val,
                        intptr_t* iter) {
   intptr_t i = *iter;
   if ((size_t)(i + 1) <= t->array_size) {
-    while (++i < t->array_size) {
+    while ((size_t)++i < t->array_size) {
       upb_tabval ent = t->array[i];
       if (upb_arrhas(ent)) {
         *key = i;
@@ -802,7 +802,7 @@ bool upb_inttable_next(const upb_inttable* t, uintptr_t* key, upb_value* val,
 
 void upb_inttable_removeiter(upb_inttable* t, intptr_t* iter) {
   intptr_t i = *iter;
-  if (i < t->array_size) {
+  if ((size_t)i < t->array_size) {
     t->array_count--;
     mutable_array(t)[i].val = -1;
   } else {
diff --git a/upb/mini_table/common.c b/upb/mini_table/common.c
index 2c4c911963..34c7c91cf1 100644
--- a/upb/mini_table/common.c
+++ b/upb/mini_table/common.c
@@ -68,7 +68,7 @@ const upb_MiniTableField* upb_MiniTable_FindFieldByNumber(
   int hi = t->field_count - 1;
   while (lo <= hi) {
     int mid = (lo + hi) / 2;
-    int num = t->fields[mid].number;
+    uint32_t num = t->fields[mid].number;
     if (num < number) {
       lo = mid + 1;
       continue;
diff --git a/upb/mini_table/decode.c b/upb/mini_table/decode.c
index 02d70132cc..976471c0c7 100644
--- a/upb/mini_table/decode.c
+++ b/upb/mini_table/decode.c
@@ -244,14 +244,14 @@ static void upb_MiniTable_SetField(upb_MtDecoder* d, uint8_t ch,
     field->offset = kHasbitPresence;
     if (type == kUpb_EncodedType_Group || type == kUpb_EncodedType_Message) {
       field->mode |= pointer_rep << kUpb_FieldRep_Shift;
-    } else if (type >= sizeof(kUpb_EncodedToFieldRep)) {
+    } else if ((unsigned long)type >= sizeof(kUpb_EncodedToFieldRep)) {
       upb_MtDecoder_ErrorFormat(d, "Invalid field type: %d", (int)type);
       UPB_UNREACHABLE();
     } else {
       field->mode |= kUpb_EncodedToFieldRep[type] << kUpb_FieldRep_Shift;
     }
   }
-  if (type >= sizeof(kUpb_EncodedToType)) {
+  if ((unsigned long)type >= sizeof(kUpb_EncodedToType)) {
     upb_MtDecoder_ErrorFormat(d, "Invalid field type: %d", (int)type);
     UPB_UNREACHABLE();
   }
@@ -667,7 +667,7 @@ static void upb_MtDecoder_AssignOffsets(upb_MtDecoder* d) {
 
 static void upb_MtDecoder_ValidateEntryField(upb_MtDecoder* d,
                                              const upb_MiniTableField* f,
-                                             int expected_num) {
+                                             uint32_t expected_num) {
   const char* name = expected_num == 1 ? "key" : "val";
   if (f->number != expected_num) {
     upb_MtDecoder_ErrorFormat(d,
diff --git a/upb/wire/decode.c b/upb/wire/decode.c
index 852052f9cd..fde4e4bbbf 100644
--- a/upb/wire/decode.c
+++ b/upb/wire/decode.c
@@ -887,7 +887,7 @@ static const upb_MiniTableField* _upb_Decoder_FindField(upb_Decoder* d,
   if (t->dense_below < t->field_count) {
     /* Linear search non-dense fields. Resume scanning from last_field_index
      * since fields are usually in order. */
-    int last = *last_field_index;
+    size_t last = *last_field_index;
     for (idx = last; idx < t->field_count; idx++) {
       if (t->fields[idx].number == field_number) {
         goto found;