diff --git a/package.json b/package.json
index 28cdb72..6a01c03 100644
--- a/package.json
+++ b/package.json
@@ -55,12 +55,12 @@
     "hyparquet": "1.20.0"
   },
   "devDependencies": {
-    "@babel/eslint-parser": "7.28.4",
+    "@babel/eslint-parser": "7.28.5",
     "@types/node": "24.9.1",
-    "@vitest/coverage-v8": "3.2.4",
+    "@vitest/coverage-v8": "4.0.2",
     "eslint": "9.38.0",
-    "eslint-plugin-jsdoc": "61.1.5",
+    "eslint-plugin-jsdoc": "61.1.7",
     "typescript": "5.9.3",
-    "vitest": "3.2.4"
+    "vitest": "4.0.2"
   }
 }
diff --git a/src/thrift.js b/src/thrift.js
index 845e327..105353e 100644
--- a/src/thrift.js
+++ b/src/thrift.js
@@ -28,8 +28,13 @@ export function serializeTCompactProtocol(writer, data) {
     if (delta <= 0) {
       throw new Error(`thrift non-monotonic field ID: fid=${fid}, lastFid=${lastFid}`)
     }
-    // High nibble = delta, low nibble = type
-    writer.appendUint8(delta << 4 | type)
+    // high nibble = delta, low nibble = type < 15 or zigzag
+    if (delta <= 15) {
+      writer.appendUint8(delta << 4 | type)
+    } else {
+      writer.appendUint8(type)
+      writer.appendVarInt(fid << 1 ^ fid >> 15) // zigzag
+    }
 
     // Write the field content itself
     writeElement(writer, type, value)
@@ -137,7 +142,12 @@ function writeElement(writer, type, value) {
       if (delta <= 0) {
         throw new Error(`Non-monotonic fid in struct: fid=${fid}, lastFid=${lastFid}`)
       }
-      writer.appendUint8(delta << 4 | t & 0x0f)
+      if (delta <= 15) {
+        writer.appendUint8(delta << 4 | t)
+      } else {
+        writer.appendUint8(t)
+        writer.appendVarInt(fid << 1 ^ fid >> 15)
+      }
       writeElement(writer, t, v)
       lastFid = fid
     }
diff --git a/test/thrift.test.js b/test/thrift.test.js
index d54114a..967f3db 100644
--- a/test/thrift.test.js
+++ b/test/thrift.test.js
@@ -2,6 +2,7 @@ import { deserializeTCompactProtocol } from 'hyparquet/src/thrift.js'
 import { describe, expect, it } from 'vitest'
 import { serializeTCompactProtocol } from '../src/thrift.js'
 import { ByteWriter } from '../src/bytewriter.js'
+import { logicalType } from '../src/metadata.js'
 
 /**
  * Utility to decode a Thrift-serialized buffer and return the parsed object.
@@ -30,8 +31,7 @@ describe('serializeTCompactProtocol', () => {
 
     const writer = new ByteWriter()
     serializeTCompactProtocol(writer, data)
-    const buf = writer.buffer.slice(0, writer.offset)
-    const result = roundTripDeserialize(buf)
+    const result = roundTripDeserialize(writer.getBuffer())
 
     expect(result.field_1).toBe(true)
     expect(result.field_2).toBe(false)
@@ -61,8 +61,7 @@ describe('serializeTCompactProtocol', () => {
 
     const writer = new ByteWriter()
     serializeTCompactProtocol(writer, data)
-    const buf = writer.buffer.slice(0, writer.offset)
-    const result = roundTripDeserialize(buf)
+    const result = roundTripDeserialize(writer.getBuffer())
 
     expect(result.field_1.field_1).toBe(42)
     expect(result.field_1.field_2.field_1).toBe(true)
@@ -74,13 +73,12 @@ describe('serializeTCompactProtocol', () => {
     const data = {}
     const writer = new ByteWriter()
     serializeTCompactProtocol(writer, data)
-    const buf = writer.buffer.slice(0, writer.offset)
-    const arr = new Uint8Array(buf)
+    const arr = new Uint8Array(writer.getBuffer())
     // The entire buffer should just be [0x00] = STOP
     expect(arr).toEqual(new Uint8Array([0x00]))
 
     // Round-trip: should deserialize to an empty object
-    const result = roundTripDeserialize(buf)
+    const result = roundTripDeserialize(writer.getBuffer())
     expect(result).toEqual({})
   })
 
@@ -92,4 +90,21 @@ describe('serializeTCompactProtocol', () => {
     const writer = new ByteWriter()
     expect(() => serializeTCompactProtocol(writer, invalidData)).toThrow()
   })
+
+  it('serializes field IDs with gaps larger than 15', () => {
+    const data = { field_1: 1, field_17: 17 }
+    const writer = new ByteWriter()
+    serializeTCompactProtocol(writer, data)
+    const result = roundTripDeserialize(writer.getBuffer())
+    expect(result.field_1).toBe(1)
+    expect(result.field_17).toBe(17)
+  })
+
+  it('serializes GEOMETRY logicalType struct with field_17', () => {
+    const data = { field_1: logicalType({ type: 'GEOMETRY' }) }
+    const writer = new ByteWriter()
+    serializeTCompactProtocol(writer, data)
+    const result = roundTripDeserialize(writer.getBuffer())
+    expect(result.field_1.field_17).toEqual({})
+  })
 })