diff --git a/packages/gatsby-plugin-postcss/package.json b/packages/gatsby-plugin-postcss/package.json
index ae73975455c0d..3196534fa7ca4 100644
--- a/packages/gatsby-plugin-postcss/package.json
+++ b/packages/gatsby-plugin-postcss/package.json
@@ -8,7 +8,7 @@
   },
   "dependencies": {
     "@babel/runtime": "^7.11.2",
-    "postcss-loader": "^4.0.2"
+    "postcss-loader": "^4.0.4"
   },
   "devDependencies": {
     "@babel/cli": "^7.11.6",
diff --git a/yarn.lock b/yarn.lock
index 1c3b5f9ea4fa4..0e7daa8202146 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -3818,7 +3818,7 @@
   resolved "https://registry.yarnpkg.com/@types/joi/-/joi-14.3.4.tgz#eed1e14cbb07716079c814138831a520a725a1e0"
   integrity sha512-1TQNDJvIKlgYXGNIABfgFp9y0FziDpuGrd799Q5RcnsDu+krD+eeW/0Fs5PHARvWWFelOhIG2OPCo6KbadBM4A==
 
-"@types/json-schema@*", "@types/json-schema@^7.0.3", "@types/json-schema@^7.0.5":
+"@types/json-schema@*", "@types/json-schema@^7.0.3", "@types/json-schema@^7.0.5", "@types/json-schema@^7.0.6":
   version "7.0.6"
   resolved "https://registry.yarnpkg.com/@types/json-schema/-/json-schema-7.0.6.tgz#f4c7ec43e81b319a9815115031709f26987891f0"
   integrity sha512-3c+yGKvVP5Y9TYBEibGNR+kLtijnj7mYrXRg+WpFb2X9xm04g/DXYkfg4hmzJQosc9snFNUPkbYIhu+KAm6jJw==
@@ -4727,10 +4727,10 @@ ajv@^5.2.3, ajv@^5.3.0:
     fast-json-stable-stringify "^2.0.0"
     json-schema-traverse "^0.3.0"
 
-ajv@^6.1.0, ajv@^6.10.0, ajv@^6.10.2, ajv@^6.12.4, ajv@^6.5.0, ajv@^6.5.5, ajv@^6.9.1:
-  version "6.12.5"
-  resolved "https://registry.yarnpkg.com/ajv/-/ajv-6.12.5.tgz#19b0e8bae8f476e5ba666300387775fb1a00a4da"
-  integrity sha512-lRF8RORchjpKG50/WFf8xmg7sgCLFiYNNnqdKflk63whMQcWR5ngGjiSXkL9bjxy6B2npOK2HSMN49jEBMSkag==
+ajv@^6.1.0, ajv@^6.10.0, ajv@^6.10.2, ajv@^6.12.4, ajv@^6.12.5, ajv@^6.5.0, ajv@^6.5.5, ajv@^6.9.1:
+  version "6.12.6"
+  resolved "https://registry.yarnpkg.com/ajv/-/ajv-6.12.6.tgz#baf5a62e802b07d977034586f8c3baf5adf26df4"
+  integrity sha512-j3fVLgvTo527anyYyJOGTYJbG+vnnQYvE0m5mmkc1TK+nxAppkCLMIL0aZ4dblVCNoGShhm+kzE4ZUykBoMg4g==
   dependencies:
     fast-deep-equal "^3.1.1"
     fast-json-stable-stringify "^2.0.0"
@@ -14995,7 +14995,7 @@ kleur@^3.0.3:
   resolved "https://registry.yarnpkg.com/kleur/-/kleur-3.0.3.tgz#a79c9ecc86ee1ce3fa6206d1216c501f147fc07e"
   integrity sha512-eTIzlVOSUR+JxdDFepEYcBMtZ9Qqdef+rnzWdRZuMbOywu5tO2w2N7rqjoANZ5k9vywhL6Br1VRjUIgTQx4E8w==
 
-klona@^2.0.3:
+klona@^2.0.4:
   version "2.0.4"
   resolved "https://registry.yarnpkg.com/klona/-/klona-2.0.4.tgz#7bb1e3affb0cb8624547ef7e8f6708ea2e39dfc0"
   integrity sha512-ZRbnvdg/NxqzC7L9Uyqzf4psi1OM4Cuc+sJAkQPjO6XkQIJTNbfK2Rsmbw8fx1p2mkZdp2FZYo2+LwXYY/uwIA==
@@ -18894,15 +18894,15 @@ postcss-loader@^3.0.0:
     postcss-load-config "^2.0.0"
     schema-utils "^1.0.0"
 
-postcss-loader@^4.0.2:
-  version "4.0.2"
-  resolved "https://registry.yarnpkg.com/postcss-loader/-/postcss-loader-4.0.2.tgz#b9e55a6126ee67bb7b94bbfcbf1aa24c69f11229"
-  integrity sha512-u7Qoa6GSPIeg9/hHbNnXspzuD5jjCIWKgk1fJ/gGJPS0uaj6Whk2zjXhDAiHZyYSrDmIzUQk7GgwRF22eRIQGQ==
+postcss-loader@^4.0.4:
+  version "4.0.4"
+  resolved "https://registry.yarnpkg.com/postcss-loader/-/postcss-loader-4.0.4.tgz#b2d005b52e008a44991cf8123bee207e635eb53e"
+  integrity sha512-pntA9zIR14drQo84yGTjQJg1m7T0DkXR4vXYHBngiRZdJtEeCrojL6lOpqUanMzG375lIJbT4Yug85zC/AJWGw==
   dependencies:
     cosmiconfig "^7.0.0"
-    klona "^2.0.3"
+    klona "^2.0.4"
     loader-utils "^2.0.0"
-    schema-utils "^2.7.1"
+    schema-utils "^3.0.0"
     semver "^7.3.2"
 
 postcss-merge-longhand@^4.0.11:
@@ -22229,7 +22229,7 @@ schema-utils@^1.0.0:
     ajv-errors "^1.0.0"
     ajv-keywords "^3.1.0"
 
-schema-utils@^2.6.5, schema-utils@^2.6.6, schema-utils@^2.7.0, schema-utils@^2.7.1:
+schema-utils@^2.6.5, schema-utils@^2.6.6, schema-utils@^2.7.0:
   version "2.7.1"
   resolved "https://registry.yarnpkg.com/schema-utils/-/schema-utils-2.7.1.tgz#1ca4f32d1b24c590c203b8e7a50bf0ea4cd394d7"
   integrity sha512-SHiNtMOUGWBQJwzISiVYKu82GiV4QYGePp3odlY1tuKO7gPtphAT5R/py0fA6xtbgLL/RvtJZnU9b8s0F1q0Xg==
@@ -22238,6 +22238,15 @@ schema-utils@^2.6.5, schema-utils@^2.6.6, schema-utils@^2.7.0, schema-utils@^2.7
     ajv "^6.12.4"
     ajv-keywords "^3.5.2"
 
+schema-utils@^3.0.0:
+  version "3.0.0"
+  resolved "https://registry.yarnpkg.com/schema-utils/-/schema-utils-3.0.0.tgz#67502f6aa2b66a2d4032b4279a2944978a0913ef"
+  integrity sha512-6D82/xSzO094ajanoOSbe4YvXWMfn2A//8Y1+MUqFAJul5Bs+yn36xbK9OtNDcRVSBJ9jjeoXftM6CfztsjOAA==
+  dependencies:
+    "@types/json-schema" "^7.0.6"
+    ajv "^6.12.5"
+    ajv-keywords "^3.5.2"
+
 schemes@^1.0.1:
   version "1.1.1"
   resolved "https://registry.yarnpkg.com/schemes/-/schemes-1.1.1.tgz#41ac81335e426b429848262239334fa8b5c4ed57"