diff --git a/package.json b/package.json
index 4be89e4..f9cb37c 100644
--- a/package.json
+++ b/package.json
@@ -37,15 +37,15 @@
   "dependencies": {
     "class-is": "^1.1.0",
     "multibase": "~0.6.0",
-    "multicodec": "~0.5.1",
-    "multihashes": "~0.4.14"
+    "multicodec": "^1.0.0",
+    "multihashes": "~0.4.15"
   },
   "devDependencies": {
-    "aegir": "^18.2.0",
+    "aegir": "^20.5.0",
     "chai": "^4.2.0",
     "dirty-chai": "^2.0.1",
     "multihashing": "~0.3.3",
-    "multihashing-async": "~0.7.0"
+    "multihashing-async": "~0.8.0"
   },
   "engines": {
     "node": ">=4.0.0",
diff --git a/src/cid-util.js b/src/cid-util.js
index 8adfdd7..8a132ab 100644
--- a/src/cid-util.js
+++ b/src/cid-util.js
@@ -26,10 +26,10 @@ var CIDUtil = {
 
     if (other.version === 0) {
       if (other.codec !== 'dag-pb') {
-        return `codec must be 'dag-pb' for CIDv0`
+        return "codec must be 'dag-pb' for CIDv0"
       }
       if (other.multibaseName !== 'base58btc') {
-        return `multibaseName must be 'base58btc' for CIDv0`
+        return "multibaseName must be 'base58btc' for CIDv0"
       }
     }
 
diff --git a/src/index.js b/src/index.js
index 58a86fd..71d33bf 100644
--- a/src/index.js
+++ b/src/index.js
@@ -281,7 +281,7 @@ class CID {
    * @returns {void}
    */
   static validateCID (other) {
-    let errorMsg = CIDUtil.checkCIDComponents(other)
+    const errorMsg = CIDUtil.checkCIDComponents(other)
     if (errorMsg) {
       throw new Error(errorMsg)
     }
diff --git a/test/helpers/gen-cid.js b/test/helpers/gen-cid.js
index 831baf3..bee8d2c 100644
--- a/test/helpers/gen-cid.js
+++ b/test/helpers/gen-cid.js
@@ -1,3 +1,4 @@
+/* eslint-disable no-console */
 'use strict'
 
 // CID String: <mbase><version><mcodec><mhash>
diff --git a/test/index.spec.js b/test/index.spec.js
index 088259b..3f7ed6c 100644
--- a/test/index.spec.js
+++ b/test/index.spec.js
@@ -63,13 +63,13 @@ describe('CID', () => {
     it('throws on trying to create a CIDv0 with a codec other than dag-pb', () => {
       expect(
         () => new CID(0, 'dag-cbor', hash)
-      ).to.throw(`codec must be 'dag-pb' for CIDv0`)
+      ).to.throw("codec must be 'dag-pb' for CIDv0")
     })
 
     it('throws on trying to create a CIDv0 with a base other than base58btc', () => {
       expect(
         () => new CID(0, 'dag-pb', hash, 'base32')
-      ).to.throw(`multibaseName must be 'base58btc' for CIDv0`)
+      ).to.throw("multibaseName must be 'base58btc' for CIDv0")
     })
 
     it('throws on trying to base encode CIDv0 in other base than base58btc', () => {
@@ -345,7 +345,9 @@ describe('CID', () => {
       const hash = await multihashing(Buffer.from(`TEST${Date.now()}`), 'sha2-256')
       const cid = new CID(1, 'dag-pb', hash)
       expect(cid.buffer).to.equal(cid.buffer)
-      expect(Object.hasOwnProperty('buffer')).to.be.false()
+      // Make sure custom implementation detail properties don't leak into
+      // the prototype
+      expect(Object.prototype.hasOwnProperty.call(cid, 'buffer')).to.be.false()
     })
     it('should cache string representation when it matches the multibaseName it was constructed with', () => {
       // not string to cache yet
@@ -361,7 +363,9 @@ describe('CID', () => {
 
       // it cached!
       expect(cid.string).to.equal(base32String)
-      expect(Object.hasOwnProperty('_string')).to.be.false()
+      // Make sure custom implementation detail properties don't leak into
+      // the prototype
+      expect(Object.prototype.hasOwnProperty.call(cid, '_string')).to.be.false()
       expect(cid.toBaseEncodedString()).to.equal(base32String)
       expect(cid.toBaseEncodedString('base64')).to.equal('mAXASILp4Fr+PAc/qQUFA3l2uIiOwA2Gjlhd6nLQQ/2HyABWt')
 
diff --git a/test/profiling/cidperf-x.js b/test/profiling/cidperf-x.js
index bafc48f..340f776 100644
--- a/test/profiling/cidperf-x.js
+++ b/test/profiling/cidperf-x.js
@@ -1,3 +1,4 @@
+/* eslint-disable no-console */
 'use strict'
 
 const multihashing = require('multihashing')
@@ -44,7 +45,7 @@ console.log(`Test: Will run "new CID()" ${reps} times.`)
 // We just give ~1 second for the JS engine to start and 'rest', etc.
 // before starting new tests.
 sleep(1000).then(() => {
-  console.log(`Starting a test...`)
+  console.log('Starting a test...')
   console.time('run'); [...Array(reps).keys()].map(i => {
     cidPerf.run(i)
   })