diff --git a/examples/v2/basic2.nim b/examples/v2/basic2.nim
index d12d92d98..a17aa892c 100644
--- a/examples/v2/basic2.nim
+++ b/examples/v2/basic2.nim
@@ -37,7 +37,7 @@ proc runBackground() {.async.} =
 
   # Publish to a topic
   let payload = cast[seq[byte]]("hello world")
-  let message = WakuMessage(payload: payload, contentTopic: "foo")
+  let message = WakuMessage(payload: payload, contentTopic: ContentTopic(1))
   node.publish(topic, message)
 
 # TODO Await with try/except here
diff --git a/examples/v2/chat2.nim b/examples/v2/chat2.nim
index b456eaabe..b91756fe0 100644
--- a/examples/v2/chat2.nim
+++ b/examples/v2/chat2.nim
@@ -3,7 +3,7 @@ when not(compileOption("threads")):
 
 import std/[tables, strformat, strutils]
 import confutils, chronicles, chronos, stew/shims/net as stewNet,
-       eth/keys, bearssl
+       eth/keys, bearssl, stew/[byteutils, endians2]
 import libp2p/[switch,                   # manage transports, a single entry point for dialing and listening
                multistream,              # tag stream with short header to identify it
                crypto/crypto,            # cryptographic functions
@@ -31,7 +31,9 @@ const Help = """
 """
 
 const DefaultTopic = "waku"
-const DefaultContentTopic = "dingpu"
+
+const Dingpu = "dingpu".toBytes
+const DefaultContentTopic = ContentTopic(uint32.fromBytes(Dingpu))
 
 # XXX Connected is a bit annoying, because incoming connections don't trigger state change
 # Could poll connection pool or something here, I suppose
diff --git a/tests/v2/test_waku_filter.nim b/tests/v2/test_waku_filter.nim
index eaf4e290b..d0ea0b1b0 100644
--- a/tests/v2/test_waku_filter.nim
+++ b/tests/v2/test_waku_filter.nim
@@ -21,7 +21,8 @@ procSuite "Waku Filter":
     let
       key = PrivateKey.random(ECDSA, rng[]).get()
       peer = PeerInfo.init(key)
-      post = WakuMessage(payload: @[byte 1, 2, 3], contentTopic: "pew2")
+      contentTopic = ContentTopic(1)
+      post = WakuMessage(payload: @[byte 1, 2, 3], contentTopic: contentTopic)
 
     var dialSwitch = newStandardSwitch()
     discard await dialSwitch.start()
@@ -38,7 +39,7 @@ procSuite "Waku Filter":
 
     let
       proto = WakuFilter.init(dialSwitch, crypto.newRng(), handle)
-      rpc = FilterRequest(contentFilters: @[ContentFilter(topics: @["pew", "pew2"])], topic: "topic")
+      rpc = FilterRequest(contentFilters: @[ContentFilter(topics: @[contentTopic])], topic: "topic")
 
     dialSwitch.mount(proto)
     proto.setPeer(listenSwitch.peerInfo)
diff --git a/tests/v2/test_waku_store.nim b/tests/v2/test_waku_store.nim
index 2c4603059..95c5bee1f 100644
--- a/tests/v2/test_waku_store.nim
+++ b/tests/v2/test_waku_store.nim
@@ -20,8 +20,9 @@ procSuite "Waku Store":
     let
       key = PrivateKey.random(ECDSA, rng[]).get()
       peer = PeerInfo.init(key)
-      msg = WakuMessage(payload: @[byte 1, 2, 3], contentTopic: "topic")
-      msg2 = WakuMessage(payload: @[byte 1, 2, 3], contentTopic: "topic2")
+      topic = ContentTopic(1)
+      msg = WakuMessage(payload: @[byte 1, 2, 3], contentTopic: topic)
+      msg2 = WakuMessage(payload: @[byte 1, 2, 3], contentTopic: ContentTopic(2))
 
     var dialSwitch = newStandardSwitch()
     discard await dialSwitch.start()
@@ -32,7 +33,7 @@ procSuite "Waku Store":
     let
       proto = WakuStore.init(dialSwitch, crypto.newRng())
       subscription = proto.subscription()
-      rpc = HistoryQuery(topics: @["topic"])
+      rpc = HistoryQuery(topics: @[topic])
 
     proto.setPeer(listenSwitch.peerInfo)
 
diff --git a/tests/v2/test_wakunode.nim b/tests/v2/test_wakunode.nim
index e1752c562..026680168 100644
--- a/tests/v2/test_wakunode.nim
+++ b/tests/v2/test_wakunode.nim
@@ -19,7 +19,7 @@ procSuite "WakuNode":
       node = WakuNode.init(nodeKey, ValidIpAddress.init("0.0.0.0"),
         Port(60000))
       pubSubTopic = "chat"
-      contentTopic = "foobar"
+      contentTopic = ContentTopic(1)
       filterRequest = FilterRequest(topic: pubSubTopic, contentFilters: @[ContentFilter(topics: @[contentTopic])])
       message = WakuMessage(payload: "hello world".toBytes(),
         contentTopic: contentTopic)
@@ -71,7 +71,7 @@ procSuite "WakuNode":
       node2 = WakuNode.init(nodeKey2, ValidIpAddress.init("0.0.0.0"),
         Port(60002))
       pubSubTopic = "chat"
-      contentTopic = "foobar"
+      contentTopic = ContentTopic(1)
       filterRequest = FilterRequest(topic: pubSubTopic, contentFilters: @[ContentFilter(topics: @[contentTopic])])
       message = WakuMessage(payload: "hello world".toBytes(),
         contentTopic: contentTopic)
@@ -133,7 +133,7 @@ procSuite "WakuNode":
       nodeKey2 = crypto.PrivateKey.random(Secp256k1, rng[])[]
       node2 = WakuNode.init(nodeKey2, ValidIpAddress.init("0.0.0.0"),
         Port(60002))
-      contentTopic = "foobar"
+      contentTopic = ContentTopic(1)
       message = WakuMessage(payload: "hello world".toBytes(), contentTopic: contentTopic)
 
     var completionFut = newFuture[bool]()
@@ -169,7 +169,7 @@ procSuite "WakuNode":
       nodeKey2 = crypto.PrivateKey.random(Secp256k1, rng[])[]
       node2 = WakuNode.init(nodeKey2, ValidIpAddress.init("0.0.0.0"),
         Port(60002))
-      contentTopic = "foobar"
+      contentTopic = ContentTopic(1)
       message = WakuMessage(payload: "hello world".toBytes(), contentTopic: contentTopic)
 
     var completionFut = newFuture[bool]()
diff --git a/waku/node/v2/rpc/wakurpc.nim b/waku/node/v2/rpc/wakurpc.nim
index 1ee8b205f..3d155b09e 100644
--- a/waku/node/v2/rpc/wakurpc.nim
+++ b/waku/node/v2/rpc/wakurpc.nim
@@ -57,17 +57,21 @@ proc setupWakuRPC*(node: WakuNode, rpcsrv: RpcServer) =
     #if not result:
     #  raise newException(ValueError, "Message could not be posted")
 
-  rpcsrv.rpc("waku_query") do(topics: seq[string]) -> bool:
+  rpcsrv.rpc("waku_query") do(topics: seq[int]) -> bool:
     debug "waku_query"
 
     # XXX: Hacky in-line handler
     proc handler(response: HistoryResponse) {.gcsafe.} =
       info "Hit response handler", messages=response.messages
 
-    await node.query(HistoryQuery(topics: topics), handler)
+    var contentTopics = newSeq[ContentTopic]()
+    for topic in topics:
+      contentTopics.add(ContentTopic(topic))
+
+    await node.query(HistoryQuery(topics: contentTopics), handler)
     return true
   
-  rpcsrv.rpc("waku_subscribe_filter") do(topic: string, contentFilters: seq[seq[string]]) -> bool:
+  rpcsrv.rpc("waku_subscribe_filter") do(topic: string, contentFilters: seq[seq[int]]) -> bool:
     debug "waku_subscribe_filter"
 
     # XXX: Hacky in-line handler
@@ -76,7 +80,10 @@ proc setupWakuRPC*(node: WakuNode, rpcsrv: RpcServer) =
 
     var filters = newSeq[ContentFilter]()
     for topics in contentFilters:
-      filters.add(ContentFilter(topics: topics))
+      var contentTopics = newSeq[ContentTopic]()
+      for topic in topics:
+        contentTopics.add(ContentTopic(topic))
+      filters.add(ContentFilter(topics: contentTopics))
 
     await node.subscribe(FilterRequest(topic: topic, contentFilters: filters), handler)
     return true
diff --git a/waku/node/v2/waku_types.nim b/waku/node/v2/waku_types.nim
index 47e0a7722..b83265425 100644
--- a/waku/node/v2/waku_types.nim
+++ b/waku/node/v2/waku_types.nim
@@ -4,25 +4,26 @@
 
 import
   std/[tables, times],
-  chronos, bearssl, stew/byteutils,
+  chronos, bearssl, stew/[byteutils, endians2],
   libp2p/[switch, peerinfo, multiaddress, crypto/crypto],
   libp2p/protobuf/minprotobuf,
   libp2p/protocols/protocol,
   libp2p/switch,
   libp2p/stream/connection,
   libp2p/protocols/pubsub/[pubsub, gossipsub],
-  nimcrypto/sha2,
-  stew/byteutils
+  nimcrypto/sha2
 
 # Common data types -----------------------------------------------------------
 
 type
+  ContentTopic* = uint32
+
   Topic* = string
   Message* = seq[byte]
 
   WakuMessage* = object
     payload*: seq[byte]
-    contentTopic*: string
+    contentTopic*: ContentTopic
 
   MessageNotificationHandler* = proc(topic: string, msg: WakuMessage): Future[void] {.gcsafe, closure.}
 
@@ -51,7 +52,7 @@ type
     direction*: bool
 
   HistoryQuery* = object
-    topics*: seq[string]
+    topics*: seq[ContentTopic]
     pagingInfo*: PagingInfo
 
   HistoryResponse* = object
@@ -102,7 +103,7 @@ type
     pushHandler*: MessagePushHandler
 
   ContentFilter* = object
-    topics*: seq[string]
+    topics*: seq[ContentTopic]
 
   ContentFilterHandler* = proc(msg: WakuMessage) {.gcsafe, closure.}
 
@@ -179,7 +180,7 @@ proc computeIndex*(msg: WakuMessage): Index =
   ## Takes a WakuMessage and returns its index
   var ctx: sha256
   ctx.init()
-  if msg.contentTopic.len != 0: # checks for non-empty contentTopic
+  if msg.contentTopic != 0: # checks for non-empty contentTopic
     ctx.update(msg.contentTopic.toBytes()) # converts the topic to bytes
   ctx.update(msg.payload)
   let digest = ctx.finish()  # computes the hash
diff --git a/waku/protocol/v2/waku_filter.nim b/waku/protocol/v2/waku_filter.nim
index 0bc79171b..ae3dd3ea9 100644
--- a/waku/protocol/v2/waku_filter.nim
+++ b/waku/protocol/v2/waku_filter.nim
@@ -40,7 +40,7 @@ proc encode*(rpc: FilterRequest): ProtoBuffer =
 proc init*(T: type ContentFilter, buffer: seq[byte]): ProtoResult[T] =
   let pb = initProtoBuffer(buffer)
 
-  var topics: seq[string]
+  var topics: seq[ContentTopic]
   discard ? pb.getRepeatedField(1, topics)
 
   ok(ContentFilter(topics: topics))
diff --git a/waku/protocol/v2/waku_store.nim b/waku/protocol/v2/waku_store.nim
index 116f11f5e..f5fa4b9e5 100644
--- a/waku/protocol/v2/waku_store.nim
+++ b/waku/protocol/v2/waku_store.nim
@@ -20,7 +20,7 @@ proc init*(T: type HistoryQuery, buffer: seq[byte]): ProtoResult[T] =
   var msg = HistoryQuery()
   let pb = initProtoBuffer(buffer)
 
-  var topics: seq[string]
+  var topics: seq[ContentTopic]
 
   discard ? pb.getRepeatedField(1, topics)