diff --git a/docs/samples/composer.json b/docs/samples/composer.json
index 250ba8d..ec86d2a 100644
--- a/docs/samples/composer.json
+++ b/docs/samples/composer.json
@@ -5,6 +5,6 @@
     },
     "require-dev": {
         "google/cloud-tools": "^0.8",
-        "phpunit/phpunit": "9.5.20"
+        "phpunit/phpunit": "9.5.21"
     }
 }
diff --git a/drive/snippets/composer.json b/drive/snippets/composer.json
index 8079e18..252955b 100644
--- a/drive/snippets/composer.json
+++ b/drive/snippets/composer.json
@@ -3,7 +3,7 @@
         "google/apiclient": "^2.0"
     },
     "require-dev": {
-        "phpunit/phpunit": "9.5.20",
+        "phpunit/phpunit": "9.5.21",
         "monolog/monolog": "^1.17"
     }
 }
diff --git a/sheets/snippets/composer.json b/sheets/snippets/composer.json
index 8079e18..252955b 100644
--- a/sheets/snippets/composer.json
+++ b/sheets/snippets/composer.json
@@ -3,7 +3,7 @@
         "google/apiclient": "^2.0"
     },
     "require-dev": {
-        "phpunit/phpunit": "9.5.20",
+        "phpunit/phpunit": "9.5.21",
         "monolog/monolog": "^1.17"
     }
 }
diff --git a/slides/snippets/composer.json b/slides/snippets/composer.json
index 2262ce3..96aa46f 100644
--- a/slides/snippets/composer.json
+++ b/slides/snippets/composer.json
@@ -3,7 +3,7 @@
         "google/apiclient": "^2.10"
     },
     "require-dev": {
-        "phpunit/phpunit": "9.5.20",
+        "phpunit/phpunit": "9.5.21",
         "monolog/monolog": "^1.17"
     }
 }