diff --git a/packages/protons-runtime/package.json b/packages/protons-runtime/package.json
index 37207a4..4a44260 100644
--- a/packages/protons-runtime/package.json
+++ b/packages/protons-runtime/package.json
@@ -126,6 +126,7 @@
     "release": "aegir release"
   },
   "dependencies": {
+    "uint8-varint": "^2.0.2",
     "uint8arraylist": "^2.4.3",
     "uint8arrays": "^4.0.6"
   },
diff --git a/packages/protons-runtime/src/utils/reader.ts b/packages/protons-runtime/src/utils/reader.ts
index a594c01..abb9767 100644
--- a/packages/protons-runtime/src/utils/reader.ts
+++ b/packages/protons-runtime/src/utils/reader.ts
@@ -1,3 +1,4 @@
+import { decodeUint8Array, encodingLength } from 'uint8-varint'
 import { readFloatLE, readDoubleLE } from './float.js'
 import { LongBits } from './longbits.js'
 import * as utf8 from './utf8.js'
@@ -304,7 +305,9 @@ export class Uint8ArrayReader implements Reader {
    * JavaScript number
    */
   uint64Number (): number {
-    return this.readLongVarint().toNumber(true)
+    const value = decodeUint8Array(this.buf, this.pos)
+    this.pos += encodingLength(value)
+    return value
   }
 
   /**
diff --git a/packages/protons-runtime/src/utils/writer.ts b/packages/protons-runtime/src/utils/writer.ts
index 9ebc6d5..1842024 100644
--- a/packages/protons-runtime/src/utils/writer.ts
+++ b/packages/protons-runtime/src/utils/writer.ts
@@ -1,3 +1,4 @@
+import { encodeUint8Array, encodingLength } from 'uint8-varint'
 import { allocUnsafe } from 'uint8arrays/alloc'
 import { fromString as uint8ArrayFromString } from 'uint8arrays/from-string'
 import { writeFloatLE, writeDoubleLE } from './float.js'
@@ -186,8 +187,7 @@ class Uint8ArrayWriter implements Writer {
    * Writes an unsigned 64 bit value as a varint
    */
   uint64Number (value: number): this {
-    const bits = LongBits.fromNumber(value)
-    return this._push(writeVarint64, bits.length(), bits)
+    return this._push(encodeUint8Array, encodingLength(value), value)
   }
 
   /**