diff --git a/.babelrc b/.babelrc
index b5bc5fa..59f0475 100644
--- a/.babelrc
+++ b/.babelrc
@@ -1,8 +1,11 @@
 {
-  "plugins": [
-    ["@babel/plugin-transform-runtime", {
-      "corejs": 3,
-      "proposals": true
+  "presets": [
+    ["@babel/preset-env", {
+      "useBuiltIns": "usage",
+      "corejs": {
+        "version": 3,
+        "proposals": true
+      }
     }]
   ]
 }
\ No newline at end of file
diff --git a/package-lock.json b/package-lock.json
index c73c7cb..c934cfe 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -2242,18 +2242,6 @@
         }
       }
     },
-    "@babel/plugin-transform-runtime": {
-      "version": "7.7.6",
-      "resolved": "https://registry.npmjs.org/@babel/plugin-transform-runtime/-/plugin-transform-runtime-7.7.6.tgz",
-      "integrity": "sha512-tajQY+YmXR7JjTwRvwL4HePqoL3DYxpYXIHKVvrOIvJmeHe2y1w4tz5qz9ObUDC9m76rCzIMPyn4eERuwA4a4A==",
-      "dev": true,
-      "requires": {
-        "@babel/helper-module-imports": "^7.7.4",
-        "@babel/helper-plugin-utils": "^7.0.0",
-        "resolve": "^1.8.1",
-        "semver": "^5.5.1"
-      }
-    },
     "@babel/plugin-transform-shorthand-properties": {
       "version": "7.8.3",
       "resolved": "https://registry.npmjs.org/@babel/plugin-transform-shorthand-properties/-/plugin-transform-shorthand-properties-7.8.3.tgz",
@@ -2551,16 +2539,6 @@
         "regenerator-runtime": "^0.13.2"
       }
     },
-    "@babel/runtime-corejs3": {
-      "version": "7.8.3",
-      "resolved": "https://registry.npmjs.org/@babel/runtime-corejs3/-/runtime-corejs3-7.8.3.tgz",
-      "integrity": "sha512-lrIU4aVbmlM/wQPzhEvzvNJskKyYptuXb0fGC0lTQTupTOYtR2Vqbu6/jf8vTr4M8Wt1nIzxVrSvPI5qESa/xA==",
-      "dev": true,
-      "requires": {
-        "core-js-pure": "^3.0.0",
-        "regenerator-runtime": "^0.13.2"
-      }
-    },
     "@babel/template": {
       "version": "7.7.4",
       "resolved": "https://registry.npmjs.org/@babel/template/-/template-7.7.4.tgz",
@@ -3625,8 +3603,7 @@
     "core-js-pure": {
       "version": "3.6.4",
       "resolved": "https://registry.npmjs.org/core-js-pure/-/core-js-pure-3.6.4.tgz",
-      "integrity": "sha512-epIhRLkXdgv32xIUFaaAry2wdxZYBi6bgM7cB136dzzXXa+dFyRLTZeLUJxnd8ShrmyVXBub63n2NHo2JAt8Cw==",
-      "dev": true
+      "integrity": "sha512-epIhRLkXdgv32xIUFaaAry2wdxZYBi6bgM7cB136dzzXXa+dFyRLTZeLUJxnd8ShrmyVXBub63n2NHo2JAt8Cw=="
     },
     "core-util-is": {
       "version": "1.0.2",
diff --git a/package.json b/package.json
index b66af9d..ea6e0ed 100644
--- a/package.json
+++ b/package.json
@@ -13,13 +13,13 @@
   "license": "ISC",
   "devDependencies": {
     "@babel/core": "^7.7.7",
-    "@babel/plugin-transform-runtime": "^7.7.6",
+    "@babel/preset-env": "^7.8.3",
     "parcel": "^1.12.4",
     "parcel-plugin-svelte": "^4.0.5",
     "svelte": "^3.16.7"
   },
   "dependencies": {
-    "@babel/runtime-corejs3": "^7.8.3",
+    "core-js-pure": "^3.6.4",
     "date-fns": "^2.9.0",
     "get-urls": "^9.2.0",
     "iter-tools": "^7.0.0-rc.0"
diff --git a/src/services/mastodon.js b/src/services/mastodon.js
index e89219f..c3e577b 100644
--- a/src/services/mastodon.js
+++ b/src/services/mastodon.js
@@ -1,5 +1,5 @@
+import Observable from 'core-js-pure/features/observable'
 import { observableToAsyncIterator } from '/services/misc.js'
-import 'core-js/es7/observable.js'
 
 const LINK_RE = /<(.+?)>; rel="(\w+)"/gi
 
diff --git a/src/services/misc.js b/src/services/misc.js
index 2230cbd..a0773b0 100644
--- a/src/services/misc.js
+++ b/src/services/misc.js
@@ -83,17 +83,16 @@ export const secondsToElapsedTime = (seconds) => {
 }
 
 export async function* mkTracksIterator(statusesIterator) {
-    // const known = new Set()
-    const knownStatus = {}
-    const knownYoutube = {}
+    const knownStatus = new Set()
+    const knownYoutube = new Set()
 
     const tracks = execPipe(
         statusesIterator,
         asyncFilter(status => {
-            if (knownStatus.hasOwnProperty(status.id)) {
+            if (knownStatus.has(status.id)) {
                 return false
             } else {
-                knownStatus[status.id] = null
+                knownStatus.add(status.id)
                 return true
             }
         }),
@@ -102,10 +101,10 @@ export async function* mkTracksIterator(statusesIterator) {
             if (!data) {
                 return false
             } else {
-                if (knownYoutube.hasOwnProperty(data.id)) {
+                if (knownYoutube.has(data.id)) {
                     return false
                 } else {
-                    knownYoutube[data.id] = null
+                    knownYoutube.add(data.id)
                     return true
                 }
             }