diff --git a/src/connection-manager/index.js b/src/connection-manager/index.js
index a35d36f5..93b3c99c 100644
--- a/src/connection-manager/index.js
+++ b/src/connection-manager/index.js
@@ -1,11 +1,15 @@
 'use strict'
 
-const assert = require('assert')
+const errcode = require('err-code')
 const mergeOptions = require('merge-options')
 const LatencyMonitor = require('latency-monitor').default
 const debug = require('debug')('libp2p:connection-manager')
 const retimer = require('retimer')
 
+const {
+  ERR_INVALID_PARAMETERS
+} = require('../errors')
+
 const defaultOptions = {
   maxConnections: Infinity,
   minConnections: 0,
@@ -38,10 +42,9 @@ class ConnectionManager {
     this._registrar = libp2p.registrar
     this._peerId = libp2p.peerInfo.id.toB58String()
     this._options = mergeOptions.call({ ignoreUndefined: true }, defaultOptions, options)
-    assert(
-      this._options.maxConnections > this._options.minConnections,
-      'Connection Manager maxConnections must be greater than minConnections'
-    )
+    if (this._options.maxConnections < this._options.minConnections) {
+      throw errcode(new Error('Connection Manager maxConnections must be greater than minConnections'), ERR_INVALID_PARAMETERS)
+    }
 
     debug('options: %j', this._options)
 
diff --git a/src/errors.js b/src/errors.js
index 89ca3439..32b21ff0 100644
--- a/src/errors.js
+++ b/src/errors.js
@@ -20,6 +20,7 @@ exports.codes = {
   ERR_HOP_REQUEST_FAILED: 'ERR_HOP_REQUEST_FAILED',
   ERR_INVALID_KEY: 'ERR_INVALID_KEY',
   ERR_INVALID_MESSAGE: 'ERR_INVALID_MESSAGE',
+  ERR_INVALID_PARAMETERS: 'ERR_INVALID_PARAMETERS',
   ERR_INVALID_PEER: 'ERR_INVALID_PEER',
   ERR_MUXER_UNAVAILABLE: 'ERR_MUXER_UNAVAILABLE',
   ERR_TIMEOUT: 'ERR_TIMEOUT',
diff --git a/src/peer-store/index.js b/src/peer-store/index.js
index 51ac5991..3fe4954e 100644
--- a/src/peer-store/index.js
+++ b/src/peer-store/index.js
@@ -1,6 +1,6 @@
 'use strict'
 
-const assert = require('assert')
+const errcode = require('err-code')
 const debug = require('debug')
 const log = debug('libp2p:peer-store')
 log.error = debug('libp2p:peer-store:error')
@@ -9,6 +9,9 @@ const { EventEmitter } = require('events')
 
 const PeerId = require('peer-id')
 const PeerInfo = require('peer-info')
+const {
+  ERR_INVALID_PARAMETERS
+} = require('../errors')
 
 /**
  * Responsible for managing known peers, as well as their addresses and metadata
@@ -46,7 +49,9 @@ class PeerStore extends EventEmitter {
    * @return {PeerInfo}
    */
   put (peerInfo, options = { silent: false }) {
-    assert(PeerInfo.isPeerInfo(peerInfo), 'peerInfo must be an instance of peer-info')
+    if (!PeerInfo.isPeerInfo(peerInfo)) {
+      throw errcode(new Error('peerInfo must be an instance of peer-info'), ERR_INVALID_PARAMETERS)
+    }
 
     let peer
     // Already know the peer?
@@ -67,7 +72,9 @@ class PeerStore extends EventEmitter {
    * @return {PeerInfo}
    */
   add (peerInfo) {
-    assert(PeerInfo.isPeerInfo(peerInfo), 'peerInfo must be an instance of peer-info')
+    if (!PeerInfo.isPeerInfo(peerInfo)) {
+      throw errcode(new Error('peerInfo must be an instance of peer-info'), ERR_INVALID_PARAMETERS)
+    }
 
     // Create new instance and add values to it
     const newPeerInfo = new PeerInfo(peerInfo.id)
@@ -105,7 +112,10 @@ class PeerStore extends EventEmitter {
    * @return {PeerInfo}
    */
   update (peerInfo) {
-    assert(PeerInfo.isPeerInfo(peerInfo), 'peerInfo must be an instance of peer-info')
+    if (!PeerInfo.isPeerInfo(peerInfo)) {
+      throw errcode(new Error('peerInfo must be an instance of peer-info'), ERR_INVALID_PARAMETERS)
+    }
+
     const id = peerInfo.id.toB58String()
     const recorded = this.peers.get(id)
 
@@ -207,7 +217,9 @@ class PeerStore extends EventEmitter {
    * @returns {void}
    */
   replace (peerInfo) {
-    assert(PeerInfo.isPeerInfo(peerInfo), 'peerInfo must be an instance of peer-info')
+    if (!PeerInfo.isPeerInfo(peerInfo)) {
+      throw errcode(new Error('peerInfo must be an instance of peer-info'), ERR_INVALID_PARAMETERS)
+    }
 
     this.remove(peerInfo.id.toB58String())
     this.add(peerInfo)
diff --git a/src/pnet/index.js b/src/pnet/index.js
index 8cd8c334..b1a70ac3 100644
--- a/src/pnet/index.js
+++ b/src/pnet/index.js
@@ -1,10 +1,13 @@
 'use strict'
 
 const pipe = require('it-pipe')
-const assert = require('assert')
+const errcode = require('err-code')
 const duplexPair = require('it-pair/duplex')
 const crypto = require('libp2p-crypto')
 const Errors = require('./errors')
+const {
+  ERR_INVALID_PARAMETERS
+} = require('../errors')
 const {
   createBoxStream,
   createUnboxStream,
@@ -40,7 +43,9 @@ class Protector {
    * @returns {*} A protected duplex iterable
    */
   async protect (connection) {
-    assert(connection, Errors.NO_HANDSHAKE_CONNECTION)
+    if (!connection) {
+      throw errcode(new Error(Errors.NO_HANDSHAKE_CONNECTION), ERR_INVALID_PARAMETERS)
+    }
 
     // Exchange nonces
     log('protecting the connection')
diff --git a/src/registrar.js b/src/registrar.js
index 45118c09..cc245485 100644
--- a/src/registrar.js
+++ b/src/registrar.js
@@ -1,10 +1,13 @@
 'use strict'
 
-const assert = require('assert')
 const debug = require('debug')
+const errcode = require('err-code')
 const log = debug('libp2p:peer-store')
 log.error = debug('libp2p:peer-store:error')
 
+const {
+  ERR_INVALID_PARAMETERS
+} = require('./errors')
 const Topology = require('libp2p-interfaces/src/topology')
 const { Connection } = require('libp2p-interfaces/src/connection')
 const PeerInfo = require('peer-info')
@@ -71,8 +74,13 @@ class Registrar {
    * @returns {void}
    */
   onConnect (peerInfo, conn) {
-    assert(PeerInfo.isPeerInfo(peerInfo), 'peerInfo must be an instance of peer-info')
-    assert(Connection.isConnection(conn), 'conn must be an instance of interface-connection')
+    if (!PeerInfo.isPeerInfo(peerInfo)) {
+      throw errcode(new Error('peerInfo must be an instance of peer-info'), ERR_INVALID_PARAMETERS)
+    }
+
+    if (!Connection.isConnection(conn)) {
+      throw errcode(new Error('conn must be an instance of interface-connection'), ERR_INVALID_PARAMETERS)
+    }
 
     const id = peerInfo.id.toB58String()
     const storedConn = this.connections.get(id)
@@ -93,7 +101,9 @@ class Registrar {
    * @returns {void}
    */
   onDisconnect (peerInfo, connection, error) {
-    assert(PeerInfo.isPeerInfo(peerInfo), 'peerInfo must be an instance of peer-info')
+    if (!PeerInfo.isPeerInfo(peerInfo)) {
+      throw errcode(new Error('peerInfo must be an instance of peer-info'), ERR_INVALID_PARAMETERS)
+    }
 
     const id = peerInfo.id.toB58String()
     let storedConn = this.connections.get(id)
@@ -116,7 +126,9 @@ class Registrar {
    * @returns {Connection}
    */
   getConnection (peerInfo) {
-    assert(PeerInfo.isPeerInfo(peerInfo), 'peerInfo must be an instance of peer-info')
+    if (!PeerInfo.isPeerInfo(peerInfo)) {
+      throw errcode(new Error('peerInfo must be an instance of peer-info'), ERR_INVALID_PARAMETERS)
+    }
 
     const connections = this.connections.get(peerInfo.id.toB58String())
     // Return the first, open connection
@@ -132,9 +144,9 @@ class Registrar {
    * @return {string} registrar identifier
    */
   register (topology) {
-    assert(
-      Topology.isTopology(topology),
-      'topology must be an instance of interfaces/topology')
+    if (!Topology.isTopology(topology)) {
+      throw errcode(new Error('topology must be an instance of interfaces/topology'), ERR_INVALID_PARAMETERS)
+    }
 
     // Create topology
     const id = (parseInt(Math.random() * 1e9)).toString(36) + Date.now()