diff --git a/upb/message/accessors.h b/upb/message/accessors.h
index 4d4ee3651685..55ce69889a6f 100644
--- a/upb/message/accessors.h
+++ b/upb/message/accessors.h
@@ -364,13 +364,14 @@ UPB_API_INLINE upb_Message* upb_Message_GetOrCreateMutableMessage(
     const upb_MiniTableField* field, upb_Arena* arena) {
   UPB_ASSERT(arena);
   UPB_ASSUME(upb_MiniTableField_CType(field) == kUpb_CType_Message);
-  upb_Message* sub_message = *UPB_PTR_AT(msg, field->offset, upb_Message*);
+  upb_Message* sub_message =
+      *UPB_PTR_AT(msg, field->UPB_ONLYBITS(offset), upb_Message*);
   if (!sub_message) {
     const upb_MiniTable* sub_mini_table = upb_MiniTableSub_Message(
         mini_table->UPB_PRIVATE(subs)[field->UPB_PRIVATE(submsg_index)]);
     UPB_ASSERT(sub_mini_table);
     sub_message = _upb_Message_New(sub_mini_table, arena);
-    *UPB_PTR_AT(msg, field->offset, upb_Message*) = sub_message;
+    *UPB_PTR_AT(msg, field->UPB_ONLYBITS(offset), upb_Message*) = sub_message;
     UPB_PRIVATE(_upb_Message_SetPresence)(msg, field);
   }
   return sub_message;
diff --git a/upb/message/internal/accessors.h b/upb/message/internal/accessors.h
index 1dccea1881f0..fd6bd2f72478 100644
--- a/upb/message/internal/accessors.h
+++ b/upb/message/internal/accessors.h
@@ -100,12 +100,12 @@ UPB_INLINE void UPB_PRIVATE(_upb_Message_SetOneofCase)(
 
 UPB_INLINE void* _upb_MiniTableField_GetPtr(upb_Message* msg,
                                             const upb_MiniTableField* field) {
-  return (char*)msg + field->offset;
+  return (char*)msg + field->UPB_ONLYBITS(offset);
 }
 
 UPB_INLINE const void* _upb_MiniTableField_GetConstPtr(
     const upb_Message* msg, const upb_MiniTableField* field) {
-  return (char*)msg + field->offset;
+  return (char*)msg + field->UPB_ONLYBITS(offset);
 }
 
 UPB_INLINE void UPB_PRIVATE(_upb_Message_SetPresence)(
diff --git a/upb/mini_descriptor/decode.c b/upb/mini_descriptor/decode.c
index 1dafe0de1e8b..dfd0413b291b 100644
--- a/upb/mini_descriptor/decode.c
+++ b/upb/mini_descriptor/decode.c
@@ -174,10 +174,10 @@ static void upb_MiniTable_SetField(upb_MtDecoder* d, uint8_t ch,
     type -= kUpb_EncodedType_RepeatedBase;
     field->UPB_PRIVATE(mode) = kUpb_FieldMode_Array;
     field->UPB_PRIVATE(mode) |= pointer_rep << kUpb_FieldRep_Shift;
-    field->offset = kNoPresence;
+    field->UPB_PRIVATE(offset) = kNoPresence;
   } else {
     field->UPB_PRIVATE(mode) = kUpb_FieldMode_Scalar;
-    field->offset = kHasbitPresence;
+    field->UPB_PRIVATE(offset) = kHasbitPresence;
     if (type == kUpb_EncodedType_Group || type == kUpb_EncodedType_Message) {
       field->UPB_PRIVATE(mode) |= pointer_rep << kUpb_FieldRep_Shift;
     } else if ((unsigned long)type >= sizeof(kUpb_EncodedToFieldRep)) {
@@ -225,7 +225,7 @@ static void upb_MtDecoder_ModifyField(upb_MtDecoder* d,
   bool required = field_modifiers & kUpb_EncodedFieldModifier_IsRequired;
 
   // Validate.
-  if ((singular || required) && field->offset != kHasbitPresence) {
+  if ((singular || required) && field->UPB_PRIVATE(offset) != kHasbitPresence) {
     upb_MdDecoder_ErrorJmp(&d->base,
                            "Invalid modifier(s) for repeated field %" PRIu32,
                            upb_MiniTableField_Number(field));
@@ -236,9 +236,9 @@ static void upb_MtDecoder_ModifyField(upb_MtDecoder* d,
         upb_MiniTableField_Number(field));
   }
 
-  if (singular) field->offset = kNoPresence;
+  if (singular) field->UPB_PRIVATE(offset) = kNoPresence;
   if (required) {
-    field->offset = kRequiredPresence;
+    field->UPB_PRIVATE(offset) = kRequiredPresence;
   }
 }
 
@@ -325,7 +325,7 @@ static const char* upb_MtDecoder_DecodeOneofField(upb_MtDecoder* d,
                            " to oneof, no such field number.",
                            field_num);
   }
-  if (f->offset != kHasbitPresence) {
+  if (f->UPB_PRIVATE(offset) != kHasbitPresence) {
     upb_MdDecoder_ErrorJmp(
         &d->base,
         "Cannot add repeated, required, or singular field %" PRIu32
@@ -340,7 +340,7 @@ static const char* upb_MtDecoder_DecodeOneofField(upb_MtDecoder* d,
     item->rep = rep;
   }
   // Prepend this field to the linked list.
-  f->offset = item->field_index;
+  f->UPB_PRIVATE(offset) = item->field_index;
   item->field_index = (f - d->fields) + kOneofBase;
   return ptr;
 }
@@ -517,7 +517,7 @@ static bool upb_MtDecoder_SortLayoutItems(upb_MtDecoder* d) {
   int n = d->table->UPB_PRIVATE(field_count);
   for (int i = 0; i < n; i++) {
     upb_MiniTableField* f = &d->fields[i];
-    if (f->offset >= kOneofBase) continue;
+    if (f->UPB_PRIVATE(offset) >= kOneofBase) continue;
     upb_LayoutItem item = {.field_index = i,
                            .rep = f->UPB_PRIVATE(mode) >> kUpb_FieldRep_Shift,
                            .type = kUpb_LayoutItemType_Field};
@@ -545,9 +545,9 @@ static void upb_MtDecoder_AssignHasbits(upb_MtDecoder* d) {
   for (int i = 0; i < n; i++) {
     upb_MiniTableField* field =
         (upb_MiniTableField*)&ret->UPB_PRIVATE(fields)[i];
-    if (field->offset == kRequiredPresence) {
+    if (field->UPB_PRIVATE(offset) == kRequiredPresence) {
       field->presence = ++last_hasbit;
-    } else if (field->offset == kNoPresence) {
+    } else if (field->UPB_PRIVATE(offset) == kNoPresence) {
       field->presence = 0;
     }
   }
@@ -561,7 +561,7 @@ static void upb_MtDecoder_AssignHasbits(upb_MtDecoder* d) {
   for (int i = 0; i < n; i++) {
     upb_MiniTableField* field =
         (upb_MiniTableField*)&ret->UPB_PRIVATE(fields)[i];
-    if (field->offset == kHasbitPresence) {
+    if (field->UPB_PRIVATE(offset) == kHasbitPresence) {
       field->presence = ++last_hasbit;
     }
   }
@@ -599,9 +599,10 @@ static void upb_MtDecoder_AssignOffsets(upb_MtDecoder* d) {
     upb_MiniTableField* f = &d->fields[item->field_index];
     while (true) {
       f->presence = ~item->offset;
-      if (f->offset == kUpb_LayoutItem_IndexSentinel) break;
-      UPB_ASSERT(f->offset - kOneofBase < d->table->UPB_PRIVATE(field_count));
-      f = &d->fields[f->offset - kOneofBase];
+      if (f->UPB_PRIVATE(offset) == kUpb_LayoutItem_IndexSentinel) break;
+      UPB_ASSERT(f->UPB_PRIVATE(offset) - kOneofBase <
+                 d->table->UPB_PRIVATE(field_count));
+      f = &d->fields[f->UPB_PRIVATE(offset) - kOneofBase];
     }
   }
 
@@ -611,14 +612,14 @@ static void upb_MtDecoder_AssignOffsets(upb_MtDecoder* d) {
     switch (item->type) {
       case kUpb_LayoutItemType_OneofField:
         while (true) {
-          uint16_t next_offset = f->offset;
-          f->offset = item->offset;
+          uint16_t next_offset = f->UPB_PRIVATE(offset);
+          f->UPB_PRIVATE(offset) = item->offset;
           if (next_offset == kUpb_LayoutItem_IndexSentinel) break;
           f = &d->fields[next_offset - kOneofBase];
         }
         break;
       case kUpb_LayoutItemType_Field:
-        f->offset = item->offset;
+        f->UPB_PRIVATE(offset) = item->offset;
         break;
       default:
         break;
@@ -689,8 +690,8 @@ static void upb_MtDecoder_ParseMap(upb_MtDecoder* d, const char* data,
   // NOTE: sync with mini_table/message_internal.h.
   const size_t kv_size = d->platform == kUpb_MiniTablePlatform_32Bit ? 8 : 16;
   const size_t hasbit_size = 8;
-  d->fields[0].offset = hasbit_size;
-  d->fields[1].offset = hasbit_size + kv_size;
+  d->fields[0].UPB_PRIVATE(offset) = hasbit_size;
+  d->fields[1].UPB_PRIVATE(offset) = hasbit_size + kv_size;
   d->table->UPB_PRIVATE(size) =
       UPB_ALIGN_UP(hasbit_size + kv_size + kv_size, 8);
 
@@ -815,7 +816,7 @@ static const char* upb_MtDecoder_DoBuildMiniTableExtension(
   upb_MiniTableField* f = &ext->UPB_PRIVATE(field);
 
   f->UPB_PRIVATE(mode) |= kUpb_LabelFlags_IsExtension;
-  f->offset = 0;
+  f->UPB_PRIVATE(offset) = 0;
   f->presence = 0;
 
   if (extendee->UPB_PRIVATE(ext) & kUpb_ExtMode_IsMessageSet) {
diff --git a/upb/mini_descriptor/internal/encode_test.cc b/upb/mini_descriptor/internal/encode_test.cc
index 498464106073..aa9979db3c27 100644
--- a/upb/mini_descriptor/internal/encode_test.cc
+++ b/upb/mini_descriptor/internal/encode_test.cc
@@ -70,8 +70,8 @@ TEST_P(MiniTableTest, AllScalarTypes) {
     const upb_MiniTableField* f = &table->UPB_PRIVATE(fields)[i];
     EXPECT_EQ(i + 1, upb_MiniTableField_Number(f));
     EXPECT_TRUE(upb_MiniTableField_IsScalar(f));
-    EXPECT_TRUE(offsets.insert(f->offset).second);
-    EXPECT_TRUE(f->offset < table->UPB_PRIVATE(size));
+    EXPECT_TRUE(offsets.insert(f->UPB_PRIVATE(offset)).second);
+    EXPECT_TRUE(f->UPB_PRIVATE(offset) < table->UPB_PRIVATE(size));
   }
   EXPECT_EQ(0, table->UPB_PRIVATE(required_count));
 }
@@ -96,8 +96,8 @@ TEST_P(MiniTableTest, AllRepeatedTypes) {
     const upb_MiniTableField* f = &table->UPB_PRIVATE(fields)[i];
     EXPECT_EQ(i + 1, upb_MiniTableField_Number(f));
     EXPECT_TRUE(upb_MiniTableField_IsArray(f));
-    EXPECT_TRUE(offsets.insert(f->offset).second);
-    EXPECT_TRUE(f->offset < table->UPB_PRIVATE(size));
+    EXPECT_TRUE(offsets.insert(f->UPB_PRIVATE(offset)).second);
+    EXPECT_TRUE(f->UPB_PRIVATE(offset) < table->UPB_PRIVATE(size));
   }
   EXPECT_EQ(0, table->UPB_PRIVATE(required_count));
 }
@@ -125,8 +125,8 @@ TEST_P(MiniTableTest, Skips) {
     EXPECT_EQ(field_numbers[i], upb_MiniTableField_Number(f));
     EXPECT_EQ(kUpb_FieldType_Float, upb_MiniTableField_Type(f));
     EXPECT_TRUE(upb_MiniTableField_IsScalar(f));
-    EXPECT_TRUE(offsets.insert(f->offset).second);
-    EXPECT_TRUE(f->offset < table->UPB_PRIVATE(size));
+    EXPECT_TRUE(offsets.insert(f->UPB_PRIVATE(offset)).second);
+    EXPECT_TRUE(f->UPB_PRIVATE(offset) < table->UPB_PRIVATE(size));
   }
   EXPECT_EQ(0, table->UPB_PRIVATE(required_count));
 }
@@ -155,13 +155,14 @@ TEST_P(MiniTableTest, AllScalarTypesOneof) {
     EXPECT_EQ(i + 1, upb_MiniTableField_Number(f));
     EXPECT_TRUE(upb_MiniTableField_IsScalar(f));
     // For a oneof all fields have the same offset.
-    EXPECT_EQ(table->UPB_PRIVATE(fields)[0].offset, f->offset);
+    EXPECT_EQ(table->UPB_PRIVATE(fields)[0].UPB_PRIVATE(offset),
+              f->UPB_PRIVATE(offset));
     // All presence fields should point to the same oneof case offset.
     size_t case_ofs = _upb_MiniTableField_OneofOffset(f);
     EXPECT_EQ(table->UPB_PRIVATE(fields)[0].presence, f->presence);
-    EXPECT_TRUE(f->offset < table->UPB_PRIVATE(size));
+    EXPECT_TRUE(f->UPB_PRIVATE(offset) < table->UPB_PRIVATE(size));
     EXPECT_TRUE(case_ofs < table->UPB_PRIVATE(size));
-    EXPECT_TRUE(case_ofs != f->offset);
+    EXPECT_TRUE(case_ofs != f->UPB_PRIVATE(offset));
   }
   EXPECT_EQ(0, table->UPB_PRIVATE(required_count));
 }
diff --git a/upb/mini_table/compat.c b/upb/mini_table/compat.c
index 23e13cef346c..e834c4f09f62 100644
--- a/upb/mini_table/compat.c
+++ b/upb/mini_table/compat.c
@@ -45,7 +45,8 @@ static upb_MiniTableEquals_Status upb_deep_check(const upb_MiniTable* src,
       return false;
     if (src_field->UPB_PRIVATE(mode) != dst_field->UPB_PRIVATE(mode))
       return false;
-    if (src_field->offset != dst_field->offset) return false;
+    if (src_field->UPB_PRIVATE(offset) != dst_field->UPB_PRIVATE(offset))
+      return false;
     if (src_field->presence != dst_field->presence) return false;
     if (src_field->UPB_PRIVATE(submsg_index) !=
         dst_field->UPB_PRIVATE(submsg_index))
diff --git a/upb/mini_table/internal/field.h b/upb/mini_table/internal/field.h
index cc0974c737b4..8d7c5e730890 100644
--- a/upb/mini_table/internal/field.h
+++ b/upb/mini_table/internal/field.h
@@ -20,7 +20,7 @@
 // LINT.IfChange(struct_definition)
 struct upb_MiniTableField {
   uint32_t UPB_ONLYBITS(number);
-  uint16_t offset;
+  uint16_t UPB_ONLYBITS(offset);
   int16_t presence;  // If >0, hasbit_index.  If <0, ~oneof_index
 
   // Indexes into `upb_MiniTable.subs`
@@ -174,6 +174,11 @@ UPB_PRIVATE(_upb_MiniTableField_Number)(const struct upb_MiniTableField* f) {
   return f->UPB_ONLYBITS(number);
 }
 
+UPB_INLINE uint16_t
+UPB_PRIVATE(_upb_MiniTableField_Offset)(const struct upb_MiniTableField* f) {
+  return f->UPB_ONLYBITS(offset);
+}
+
 UPB_INLINE size_t
 _upb_MiniTableField_OneofOffset(const struct upb_MiniTableField* f) {
   UPB_ASSERT(UPB_PRIVATE(_upb_MiniTableField_IsInOneof)(f));
diff --git a/upb/wire/decode.c b/upb/wire/decode.c
index f29829033497..f5ad1cfa46cd 100644
--- a/upb/wire/decode.c
+++ b/upb/wire/decode.c
@@ -517,7 +517,7 @@ static const char* _upb_Decoder_DecodeToArray(upb_Decoder* d, const char* ptr,
                                               const upb_MiniTableSub* subs,
                                               const upb_MiniTableField* field,
                                               wireval* val, int op) {
-  upb_Array** arrp = UPB_PTR_AT(msg, field->offset, void);
+  upb_Array** arrp = UPB_PTR_AT(msg, field->UPB_PRIVATE(offset), void);
   upb_Array* arr = *arrp;
   void* mem;
 
@@ -608,8 +608,8 @@ upb_Map* _upb_Decoder_CreateMap(upb_Decoder* d, const upb_MiniTable* entry) {
   const upb_MiniTableField* val_field = &entry->UPB_PRIVATE(fields)[1];
   char key_size = kSizeInMap[key_field->UPB_PRIVATE(descriptortype)];
   char val_size = kSizeInMap[val_field->UPB_PRIVATE(descriptortype)];
-  UPB_ASSERT(key_field->offset == offsetof(upb_MapEntryData, k));
-  UPB_ASSERT(val_field->offset == offsetof(upb_MapEntryData, v));
+  UPB_ASSERT(key_field->UPB_PRIVATE(offset) == offsetof(upb_MapEntryData, k));
+  UPB_ASSERT(val_field->UPB_PRIVATE(offset) == offsetof(upb_MapEntryData, v));
   upb_Map* ret = _upb_Map_New(&d->arena, key_size, val_size);
   if (!ret) _upb_Decoder_ErrorJmp(d, kUpb_DecodeStatus_OutOfMemory);
   return ret;
@@ -620,7 +620,7 @@ static const char* _upb_Decoder_DecodeToMap(upb_Decoder* d, const char* ptr,
                                             const upb_MiniTableSub* subs,
                                             const upb_MiniTableField* field,
                                             wireval* val) {
-  upb_Map** map_p = UPB_PTR_AT(msg, field->offset, upb_Map*);
+  upb_Map** map_p = UPB_PTR_AT(msg, field->UPB_PRIVATE(offset), upb_Map*);
   upb_Map* map = *map_p;
   upb_MapEntry ent;
   UPB_ASSERT(upb_MiniTableField_Type(field) == kUpb_FieldType_Message);
@@ -683,7 +683,7 @@ static const char* _upb_Decoder_DecodeToSubMessage(
     upb_Decoder* d, const char* ptr, upb_Message* msg,
     const upb_MiniTableSub* subs, const upb_MiniTableField* field, wireval* val,
     int op) {
-  void* mem = UPB_PTR_AT(msg, field->offset, void);
+  void* mem = UPB_PTR_AT(msg, field->UPB_PRIVATE(offset), void);
   int type = field->UPB_PRIVATE(descriptortype);
 
   if (UPB_UNLIKELY(op == kUpb_DecodeOp_Enum) &&
diff --git a/upb/wire/encode.c b/upb/wire/encode.c
index 5ec9edc8e180..4f923e9c3994 100644
--- a/upb/wire/encode.c
+++ b/upb/wire/encode.c
@@ -309,7 +309,7 @@ static void encode_scalar(upb_encstate* e, const void* _field_mem,
 static void encode_array(upb_encstate* e, const upb_Message* msg,
                          const upb_MiniTableSub* subs,
                          const upb_MiniTableField* f) {
-  const upb_Array* arr = *UPB_PTR_AT(msg, f->offset, upb_Array*);
+  const upb_Array* arr = *UPB_PTR_AT(msg, f->UPB_PRIVATE(offset), upb_Array*);
   bool packed = upb_MiniTableField_IsPacked(f);
   size_t pre_len = e->limit - e->ptr;
 
@@ -432,7 +432,7 @@ static void encode_mapentry(upb_encstate* e, uint32_t number,
 static void encode_map(upb_encstate* e, const upb_Message* msg,
                        const upb_MiniTableSub* subs,
                        const upb_MiniTableField* f) {
-  const upb_Map* map = *UPB_PTR_AT(msg, f->offset, const upb_Map*);
+  const upb_Map* map = *UPB_PTR_AT(msg, f->UPB_PRIVATE(offset), const upb_Map*);
   const upb_MiniTable* layout =
       upb_MiniTableSub_Message(subs[f->UPB_PRIVATE(submsg_index)]);
   UPB_ASSERT(layout->UPB_PRIVATE(field_count) == 2);
@@ -467,7 +467,7 @@ static bool encode_shouldencode(upb_encstate* e, const upb_Message* msg,
                                 const upb_MiniTableField* f) {
   if (f->presence == 0) {
     // Proto3 presence or map/array.
-    const void* mem = UPB_PTR_AT(msg, f->offset, void);
+    const void* mem = UPB_PTR_AT(msg, f->UPB_PRIVATE(offset), void);
     switch (UPB_PRIVATE(_upb_MiniTableField_GetRep)(f)) {
       case kUpb_FieldRep_1Byte: {
         char ch;
@@ -512,7 +512,8 @@ static void encode_field(upb_encstate* e, const upb_Message* msg,
       encode_map(e, msg, subs, field);
       break;
     case kUpb_FieldMode_Scalar:
-      encode_scalar(e, UPB_PTR_AT(msg, field->offset, void), subs, field);
+      encode_scalar(e, UPB_PTR_AT(msg, field->UPB_PRIVATE(offset), void), subs,
+                    field);
       break;
     default:
       UPB_UNREACHABLE();
diff --git a/upb_generator/common.cc b/upb_generator/common.cc
index 554c02e6cc64..9c60a7edf0c1 100644
--- a/upb_generator/common.cc
+++ b/upb_generator/common.cc
@@ -85,7 +85,8 @@ std::string FieldInitializer(upb::FieldDefPtr field,
                              const upb_MiniTableField* field32) {
   return absl::Substitute(
       "{$0, $1, $2, $3, $4, $5}", upb_MiniTableField_Number(field64),
-      ArchDependentSize(field32->offset, field64->offset),
+      ArchDependentSize(field32->UPB_PRIVATE(offset),
+                        field64->UPB_PRIVATE(offset)),
       ArchDependentSize(field32->presence, field64->presence),
       field64->UPB_PRIVATE(submsg_index) == kUpb_NoSub
           ? "kUpb_NoSub"
diff --git a/upb_generator/protoc-gen-upb_minitable.cc b/upb_generator/protoc-gen-upb_minitable.cc
index 1c5d636f2d86..d58af3a89bd1 100644
--- a/upb_generator/protoc-gen-upb_minitable.cc
+++ b/upb_generator/protoc-gen-upb_minitable.cc
@@ -286,7 +286,8 @@ bool TryFillTableEntry(const DefPoolPair& pools, upb::FieldDefPtr field,
   //
   // - |presence| is either hasbit index or field number for oneofs.
 
-  uint64_t data = static_cast<uint64_t>(mt_f->offset) << 48 | expected_tag;
+  uint64_t data =
+      static_cast<uint64_t>(mt_f->UPB_PRIVATE(offset)) << 48 | expected_tag;
 
   if (field.IsSequence()) {
     // No hasbit/oneof-related fields.