diff --git a/lib/feed-v1/validation.js b/lib/feed-v1/validation.js
index f6a9c6d..1df2006 100644
--- a/lib/feed-v1/validation.js
+++ b/lib/feed-v1/validation.js
@@ -90,6 +90,22 @@ function validateTangle(msg, tangle, tangleId) {
     // prettier-ignore
     return new Error('invalid message: prev must be an array, on feed: ' + msg.metadata.who);
   }
+  if (typeof depth !== 'number') {
+    // prettier-ignore
+    return new Error('invalid message: depth must be a number, on feed: ' + msg.metadata.who);
+  }
+  if (tangle.isFeed()) {
+    const { type, who } = tangle.getFeed()
+    if (type !== msg.metadata.type) {
+      // prettier-ignore
+      return new Error(`invalid message: type "${msg.metadata.type}" does not match feed type "${type}"`)
+    }
+    if (who !== msg.metadata.who) {
+      // prettier-ignore
+      return new Error(`invalid message: who "${msg.metadata.who}" does not match feed who "${who}"`)
+    }
+  }
+  let minDiff = Infinity
   for (const p of prev) {
     if (typeof p !== 'string') {
       // prettier-ignore
@@ -106,10 +122,16 @@ function validateTangle(msg, tangle, tangleId) {
     }
     const prevDepth = tangle.getDepth(p)
 
-    if (prevDepth >= depth) {
+    const diff = depth - prevDepth
+    if (diff <= 0) {
       // prettier-ignore
       return new Error('invalid message: depth of prev ' + p + ' is not lower, on feed: ' + msg.metadata.who);
     }
+    if (diff < minDiff) minDiff = diff
+  }
+  if (minDiff !== 1) {
+    // prettier-ignore
+    return new Error('invalid message: depth must be the largest prev depth plus one');
   }
 }
 
diff --git a/lib/tangle.js b/lib/tangle.js
index 54c3508..1c98d0d 100644
--- a/lib/tangle.js
+++ b/lib/tangle.js
@@ -2,6 +2,10 @@
  * @typedef {import("./plugin").Rec} Rec
  */
 
+/**
+ * @typedef {import("./feed-v1").Msg} Msg
+ */
+
 function lipmaa(n) {
   let m = 1
   let po3 = 3
@@ -45,6 +49,11 @@ class Tangle {
    */
   #rootHash
 
+  /**
+   * @type {Msg}
+   */
+  #rootMsg
+
   /**
    * @type {Set<string>}
    */
@@ -89,6 +98,7 @@ class Tangle {
       this.#tips.add(msgHash)
       this.#perDepth.set(0, [msgHash])
       this.#depth.set(msgHash, 0)
+      this.#rootMsg = msg
     } else if (tangles[this.#rootHash]) {
       this.#tips.add(msgHash)
       const prev = tangles[this.#rootHash].prev
@@ -162,6 +172,18 @@ class Tangle {
     return this.#depth.get(msgHash) ?? -1
   }
 
+  isFeed() {
+    if (this.#rootMsg.content) return false
+    const metadata = this.#rootMsg.metadata
+    return metadata.size === 0 && metadata.proof === ''
+  }
+
+  getFeed() {
+    if (!this.isFeed()) return null
+    const { type, who } = this.#rootMsg.metadata
+    return { type, who }
+  }
+
   #shortestPathToRoot(msgHash) {
     const path = []
     let current = msgHash
diff --git a/test/feed-v1-invalid-prev.test.js b/test/feed-v1-invalid-prev.test.js
index d72860e..596043e 100644
--- a/test/feed-v1-invalid-prev.test.js
+++ b/test/feed-v1-invalid-prev.test.js
@@ -176,3 +176,56 @@ tape('invalid msg with unknown prev', (t) => {
     t.end()
   })
 })
+
+tape('invalid feed msg with a different who', (t) => {
+  const keysA = generateKeypair('alice')
+  const keysB = generateKeypair('bob')
+
+  const rootMsg = FeedV1.createRoot(keysA, 'post')
+  const rootHash = FeedV1.getMsgHash(rootMsg)
+  const feedTangle = new Tangle(rootHash, [{ hash: rootHash, msg: rootMsg }])
+
+  const msg = FeedV1.create({
+    keys: keysB,
+    content: { text: 'Hello world!' },
+    type: 'post',
+    tangles: {
+      [rootHash]: feedTangle,
+    },
+    when: 1652030002000,
+  })
+  const msgHash = FeedV1.getMsgHash(msg)
+
+  FeedV1.validate(msg, feedTangle, msgHash, rootHash, (err) => {
+    t.match(err.message, /who ".*" does not match feed who/, 'invalid feed msg')
+    t.end()
+  })
+})
+
+tape('invalid feed msg with a different type', (t) => {
+  const keysA = generateKeypair('alice')
+
+  const rootMsg = FeedV1.createRoot(keysA, 'post')
+  const rootHash = FeedV1.getMsgHash(rootMsg)
+  const feedTangle = new Tangle(rootHash, [{ hash: rootHash, msg: rootMsg }])
+
+  const msg = FeedV1.create({
+    keys: keysA,
+    content: { text: 'Hello world!' },
+    type: 'comment',
+    tangles: {
+      [rootHash]: feedTangle,
+    },
+    when: 1652030002000,
+  })
+  const msgHash = FeedV1.getMsgHash(msg)
+
+  FeedV1.validate(msg, feedTangle, msgHash, rootHash, (err) => {
+    t.match(
+      err.message,
+      /type "comment" does not match feed type "post"/,
+      'invalid feed msg'
+    )
+    t.end()
+  })
+})