diff --git a/package.json b/package.json
index 08d5a68..0f76ab2 100644
--- a/package.json
+++ b/package.json
@@ -41,8 +41,7 @@
     "mustache": "^4.1.0",
     "mutable-buffer": "2.0.3",
     "ndarray": "^1.0.19",
-    "pngjs": "^6.0.0",
-    "upng-js": "^2.1.0",
+    "upng-js": "2.1.0",
     "xml-parser": "^1.2.1"
   },
   "devDependencies": {
diff --git a/yarn.lock b/yarn.lock
index 7141c94..59b9b90 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -366,11 +366,6 @@ path-parse@^1.0.6:
   resolved "https://registry.npmjs.org/path-parse/-/path-parse-1.0.6.tgz"
   integrity sha512-GSmOT2EbHrINBf9SR7CDELwlJ8AENk3Qn7OikK4nFYAu3Ote2+JYNVvkpAEQm3/TLNEJFD/xZJjzyxg3KBWOzw==
 
-pngjs@^6.0.0:
-  version "6.0.0"
-  resolved "https://registry.npmjs.org/pngjs/-/pngjs-6.0.0.tgz"
-  integrity sha512-TRzzuFRRmEoSW/p1KVAmiOgPco2Irlah+bGFCeNfJXxxYGwSw7YwAOAcd7X28K/m5bjBWKsC29KyoMfHbypayg==
-
 process-nextick-args@~2.0.0:
   version "2.0.1"
   resolved "https://registry.npmjs.org/process-nextick-args/-/process-nextick-args-2.0.1.tgz"
@@ -496,7 +491,7 @@ typescript@^4.1.3:
   resolved "https://registry.npmjs.org/typescript/-/typescript-4.1.3.tgz"
   integrity sha512-B3ZIOf1IKeH2ixgHhj6la6xdwR9QrLC5d1VKeCSY4tvkqhF2eqd9O7txNlS0PO3GrBAFIdr3L1ndNwteUbZLYg==
 
-upng-js@^2.1.0:
+upng-js@2.1.0:
   version "2.1.0"
   resolved "https://registry.yarnpkg.com/upng-js/-/upng-js-2.1.0.tgz#7176e73973db361ca95d0fa14f958385db6b9dd2"
   integrity sha512-d3xzZzpMP64YkjP5pr8gNyvBt7dLk/uGI67EctzDuVp4lCZyVMo0aJO6l/VDlgbInJYDY6cnClLoBp29eKWI6g==