diff --git a/test/dummy/package.json b/test/dummy/package.json
index 64b53440..3917b4c6 100644
--- a/test/dummy/package.json
+++ b/test/dummy/package.json
@@ -6,7 +6,7 @@
     "clipboard": "^2.0.1",
     "flying-focus": "^1.1.3",
     "jquery": "^3.3.1",
-    "lazysizes": "^4.1.2",
+    "lazysizes": "^5.2.1",
     "postcss-preset-env": "^6.0.10",
     "prop-types": "^15.6.2",
     "rails-ujs": "^5.2.1",
diff --git a/test/dummy/yarn.lock b/test/dummy/yarn.lock
index c680c5cf..69063f28 100644
--- a/test/dummy/yarn.lock
+++ b/test/dummy/yarn.lock
@@ -3821,10 +3821,10 @@ lazy-cache@^1.0.3:
   resolved "https://registry.yarnpkg.com/lazy-cache/-/lazy-cache-1.0.4.tgz#a1d78fc3a50474cb80845d3b3b6e1da49a446e8e"
   integrity sha1-odePw6UEdMuAhF07O24dpJpEbo4=
 
-lazysizes@^4.1.2:
-  version "4.1.7"
-  resolved "https://registry.yarnpkg.com/lazysizes/-/lazysizes-4.1.7.tgz#3e11c543c3b7695a75c15c3b9670f5f959de1151"
-  integrity sha512-icCNEAj4uQJt3MVBHo5Gx7FEuX6UYMrsS2x3M6jlUVnLGeb/K8iD4GsjCsLAlOJcpCJZgTFPozaYZboK3WigHw==
+lazysizes@^5.2.1:
+  version "5.2.1"
+  resolved "https://registry.yarnpkg.com/lazysizes/-/lazysizes-5.2.1.tgz#f450e36a995efb5817acb8c904f3d2f2efc29ffa"
+  integrity sha512-607dEMlbcnkny2lGYVqoA/rQO+WGpWh/BISeS1eLfT8nHQw6E+R8ybJoKKGVlZ2czKPTATrsU95f+nkwix0fXw==
 
 lcid@^1.0.0:
   version "1.0.0"