diff --git a/eclair-core/src/main/scala/fr/acinq/eclair/UInt64.scala b/eclair-core/src/main/scala/fr/acinq/eclair/UInt64.scala
index 97a8293d65..d709124d8e 100644
--- a/eclair-core/src/main/scala/fr/acinq/eclair/UInt64.scala
+++ b/eclair-core/src/main/scala/fr/acinq/eclair/UInt64.scala
@@ -18,26 +18,18 @@ package fr.acinq.eclair
 
 import com.google.common.primitives.UnsignedLongs
 import scodec.bits.ByteVector
-import scodec.bits._
+import scodec.bits.HexStringSyntax
 
 case class UInt64(private val underlying: Long) extends Ordered[UInt64] {
 
   override def compare(o: UInt64): Int = UnsignedLongs.compare(underlying, o.underlying)
 
-  def toByteVector: ByteVector = this match {
-    case x if x <= UInt64(255) => ByteVector.fromLong(underlying, size = 1)
-    case x if x <= UInt64(65535) => ByteVector.fromLong(underlying, size = 2)
-    case x if x <= UInt64(16777215) => ByteVector.fromLong(underlying, size = 3)
-    case x if x <= UInt64(4294967295L) => ByteVector.fromLong(underlying, size = 4)
-    case x if x <= UInt64(1099511627775L) => ByteVector.fromLong(underlying, size = 5)
-    case x if x <= UInt64(281474976710655L) => ByteVector.fromLong(underlying, size = 6)
-    case x if x <= UInt64(72057594037927935L) => ByteVector.fromLong(underlying, size = 7)
-    case _ => ByteVector.fromLong(underlying, size = 8)
+  def toByteVector: ByteVector = underlying match {
+    case 0 => hex"00"
+    case _ => ByteVector.fromLong(underlying).dropWhile(_ == 0)
   }
 
-  def toBigInt: BigInt = BigInt(toString)
-
-  def toLong: Long = underlying
+  def toBigInt: BigInt = BigInt(signum = 1, toByteVector.toArray)
 
   override def toString: String = UnsignedLongs.toString(underlying, 10)
 }
diff --git a/eclair-core/src/test/scala/fr/acinq/eclair/UInt64Spec.scala b/eclair-core/src/test/scala/fr/acinq/eclair/UInt64Spec.scala
index d1d9d77d36..b6258be587 100644
--- a/eclair-core/src/test/scala/fr/acinq/eclair/UInt64Spec.scala
+++ b/eclair-core/src/test/scala/fr/acinq/eclair/UInt64Spec.scala
@@ -27,11 +27,23 @@ class UInt64Spec extends FunSuite {
     val b = UInt64(hex"0xfffffffffffffffe")
     val c = UInt64(42)
     val z = UInt64(0)
+    val l = UInt64(Long.MaxValue)
+    val l1 = UInt64(hex"8000000000000000") // Long.MaxValue + 1
+
     assert(a > b)
+    assert(a.toBigInt > b.toBigInt)
     assert(b < a)
-    assert(z < a && z < b && z < c)
+    assert(b.toBigInt < a.toBigInt)
+    assert(l.toBigInt < l1.toBigInt)
+    assert(z < a && z < b && z < c && z < l && c < l && l < l1 && l < b && l < a)
     assert(a == a)
     assert(a == UInt64.MaxValue)
+    assert(l.toByteVector == hex"7fffffffffffffff")
+    assert(l.toString == Long.MaxValue.toString)
+    assert(l.toBigInt == BigInt(Long.MaxValue))
+    assert(l1.toByteVector == hex"8000000000000000")
+    assert(l1.toString == "9223372036854775808")
+    assert(l1.toBigInt == BigInt("9223372036854775808"))
     assert(a.toByteVector === hex"0xffffffffffffffff")
     assert(a.toString === "18446744073709551615")
     assert(b.toByteVector === hex"0xfffffffffffffffe")