diff --git a/.travis.yml b/.travis.yml
index b8fd3a5..ba786ad 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -25,5 +25,6 @@ before_install:
     export PATH=$PWD/bin:$PATH
     cd ..
 script:
+  - nimble install -y
   - nimble test
 
diff --git a/rlp.nim b/rlp.nim
index 33425ee..3968897 100644
--- a/rlp.nim
+++ b/rlp.nim
@@ -168,7 +168,7 @@ proc isInt*(self: Rlp): bool =
     return bytes[offset] != 0
   return false
 
-template maxBytes*(o: typedesc[Ordinal]): int = sizeof(o)
+template maxBytes*(o: typedesc[Ordinal | uint64 | uint]): int = sizeof(o)
 
 proc toInt*(self: Rlp, IntType: typedesc): IntType =
   # XXX: self insertions are not working in generic procs
@@ -184,7 +184,7 @@ proc toInt*(self: Rlp, IntType: typedesc): IntType =
     raise newException(BadCastError, "")
 
   for i in payloadStart ..< (payloadStart + payloadSize):
-    result = (result shl 8) or int(self.bytes[self.position + i])
+    result = cast[IntType](result shl 8) or cast[IntType](self.bytes[self.position + i])
 
 proc toString*(self: Rlp): string =
   if not isBlob():
@@ -266,8 +266,8 @@ proc read*(rlp: var Rlp, T: type string): string =
   result = rlp.toString
   rlp.skipElem
 
-proc read*(rlp: var Rlp, T: type int): int =
-  result = rlp.toInt(int)
+proc read*(rlp: var Rlp, T: type Integer): Integer =
+  result = rlp.toInt(T)
   rlp.skipElem
 
 proc read*[E](rlp: var Rlp, T: typedesc[seq[E]]): T =
@@ -306,6 +306,7 @@ proc decode*(bytes: openarray[byte]): RlpNode =
     bytesCopy = @bytes
     rlp = rlpFromBytes initBytesRange(bytesCopy)
   return rlp.toNodes
+  
 
 template decode*(bytes: BytesRange, T: typedesc): untyped =
   var rlp = rlpFromBytes bytes
diff --git a/rlp.nimble b/rlp.nimble
index 873eb76..a988cb7 100644
--- a/rlp.nimble
+++ b/rlp.nimble
@@ -7,7 +7,7 @@ description   = "RLP serialization library for Nim"
 license       = "Apache2"
 skipDirs      = @["tests"]
 
-requires "nim >= 0.17.0", "ranges >= 0.0.1"
+requires "nim >= 0.17.0", "https://github.com/status-im/nim-ranges >= 0.0.1"
 
 proc configForTests() =
   --hints: off
diff --git a/rlp/object_serialization.nim b/rlp/object_serialization.nim
index 37c43bf..2effbc8 100644
--- a/rlp/object_serialization.nim
+++ b/rlp/object_serialization.nim
@@ -15,4 +15,3 @@ macro rlpFields*(T: typedesc, fields: varargs[untyped]): untyped =
   result = quote do:
     template enumerateRlpFields*(`ins`: `T`, `op`: untyped) {.inject.} =
       `body`
-
diff --git a/rlp/writer.nim b/rlp/writer.nim
index 471b642..e508928 100644
--- a/rlp/writer.nim
+++ b/rlp/writer.nim
@@ -13,18 +13,17 @@ type
 
   PrematureFinalizationError* = object of Exception
 
-  IntLike* = concept x, y
-    x + y
-    x * y
-    x - y
-    x div y
-    x mod y
-    x shr y
-    x shl y
+  IntLike* = concept x, y, type T
+    x + y is T
+    x * y is T
+    x - y is T
+    x div y is T
+    x mod y is T
+    x shr y is T
+    x shl y is T
     x and int # for masking
 
-  # Integer* = SomeOrdinal or IntLike
-  Integer = int
+  Integer* = SomeOrdinal or IntLike or uint or uint64
 
 proc bytesNeeded(num: Integer): int =
   var n = num
@@ -154,7 +153,7 @@ proc append*(self; data: MemRange) =
 proc append*(self; i: Integer) =
   if i == 0:
     self.output.add BLOB_START_MARKER
-  elif i < Integer(BLOB_START_MARKER):
+  elif i < BLOB_START_MARKER.Integer:
     self.output.add byte(i)
   else:
     let bytesNeeded = i.bytesNeeded
diff --git a/tests/test_object_serialization.nim b/tests/test_object_serialization.nim
index 356158b..f42ff9e 100644
--- a/tests/test_object_serialization.nim
+++ b/tests/test_object_serialization.nim
@@ -9,7 +9,7 @@ type
     receiver: string
 
   Foo = object
-    x: int
+    x: uint64
     y: string
     z: seq[int]
 
@@ -27,7 +27,7 @@ proc default(T: typedesc): T = discard
 
 test "encoding and decoding an object":
   var originalBar = Bar(b: "abracadabra",
-                        f: Foo(x: 5, y: "hocus pocus", z: @[100, 200, 300]))
+                        f: Foo(x: 5'u64, y: "hocus pocus", z: @[100, 200, 300]))
 
   var bytes = encode(originalBar)