diff --git a/package-lock.json b/package-lock.json
index 02d25735..4773fc5d 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -5,9 +5,9 @@
   "requires": true,
   "dependencies": {
     "@openzeppelin/contracts": {
-      "version": "3.3.0",
-      "resolved": "https://registry.npmjs.org/@openzeppelin/contracts/-/contracts-3.3.0.tgz",
-      "integrity": "sha512-AemZEsQYtUp1WRkcmZm1div5ORfTpLquLaziCIrSagjxyKdmObxuaY1yjQ5SHFMctR8rLwp706NXTbiIRJg7pw=="
+      "version": "4.7.2",
+      "resolved": "https://registry.npmjs.org/@openzeppelin/contracts/-/contracts-4.7.2.tgz",
+      "integrity": "sha512-4n/JL9izql8303mPqPdubuna/DWEMbmOzWYUWyCPhjhiEr2w3nQrjE7vZz1fBF+wzzP6dZbIcsgqACk53c9FGA=="
     },
     "abstract-leveldown": {
       "version": "2.6.3",
diff --git a/package.json b/package.json
index 30f04e26..b9469270 100644
--- a/package.json
+++ b/package.json
@@ -12,7 +12,7 @@
   "author": "",
   "license": "",
   "dependencies": {
-    "@openzeppelin/contracts": "^3.3.0",
+    "@openzeppelin/contracts": "^4.7.2",
     "bignumber.js": "^6.0.0",
     "chai": "^4.1.2",
     "chai-as-promised": "^7.1.1",
diff --git a/yarn.lock b/yarn.lock
index cf665a98..4e08058f 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -2,10 +2,10 @@
 # yarn lockfile v1
 
 
-"@openzeppelin/contracts@^3.3.0":
-  version "3.4.0"
-  resolved "https://registry.yarnpkg.com/@openzeppelin/contracts/-/contracts-3.4.0.tgz#9a1669ad5f9fdfb6e273bb5a4fed10cb4cc35eb0"
-  integrity sha512-qh+EiHWzfY/9CORr+eRUkeEUP1WiFUcq3974bLHwyYzLBUtK6HPaMkIUHi74S1rDTZ0sNz42DwPc5A4IJvN3rg==
+"@openzeppelin/contracts@^4.7.2":
+  version "4.7.2"
+  resolved "https://registry.yarnpkg.com/@openzeppelin/contracts/-/contracts-4.7.2.tgz#7587416fe2d35abf574193515b8971bfe9f64bc7"
+  integrity sha512-4n/JL9izql8303mPqPdubuna/DWEMbmOzWYUWyCPhjhiEr2w3nQrjE7vZz1fBF+wzzP6dZbIcsgqACk53c9FGA==
 
 "@types/bn.js@^4.11.3":
   version "4.11.6"
@@ -96,8 +96,9 @@ async-eventemitter@^0.2.2:
   dependencies:
     async "^2.4.0"
 
-"async-eventemitter@github:ahultgren/async-eventemitter#fa06e39e56786ba541c180061dbf2c0a5bbf951c":
+async-eventemitter@ahultgren/async-eventemitter#fa06e39e56786ba541c180061dbf2c0a5bbf951c:
   version "0.2.3"
+  uid fa06e39e56786ba541c180061dbf2c0a5bbf951c
   resolved "https://codeload.github.com/ahultgren/async-eventemitter/tar.gz/fa06e39e56786ba541c180061dbf2c0a5bbf951c"
   dependencies:
     async "^2.4.0"
@@ -814,13 +815,14 @@ bignumber.js@^6.0.0:
   resolved "https://registry.yarnpkg.com/bignumber.js/-/bignumber.js-6.0.0.tgz#bbfa047644609a5af093e9cbd83b0461fa3f6002"
   integrity sha512-x247jIuy60/+FtMRvscqfxtVHQf8AGx2hm9c6btkgC0x/hp9yt+teISNhvF8WlwRkCc5yF2fDECH8SIMe8j+GA==
 
-"bignumber.js@git+https://github.com/debris/bignumber.js.git#94d7146671b9719e00a09c29b01a691bc85048c2":
+"bignumber.js@git+https://github.com/debris/bignumber.js#master":
   version "2.0.7"
-  resolved "git+https://github.com/debris/bignumber.js.git#94d7146671b9719e00a09c29b01a691bc85048c2"
+  uid c7a38de919ed75e6fb6ba38051986e294b328df9
+  resolved "git+https://github.com/debris/bignumber.js#c7a38de919ed75e6fb6ba38051986e294b328df9"
 
-"bignumber.js@git+https://github.com/debris/bignumber.js.git#master":
+"bignumber.js@git+https://github.com/debris/bignumber.js.git#94d7146671b9719e00a09c29b01a691bc85048c2":
   version "2.0.7"
-  resolved "git+https://github.com/debris/bignumber.js.git#c7a38de919ed75e6fb6ba38051986e294b328df9"
+  resolved "git+https://github.com/debris/bignumber.js.git#94d7146671b9719e00a09c29b01a691bc85048c2"
 
 "bignumber.js@git+https://github.com/frozeman/bignumber.js-nolookahead.git":
   version "2.0.7"