diff --git a/tests/Composer/Test/Fixtures/installer/install-dev-using-dist.test b/tests/Composer/Test/Fixtures/installer/install-dev-using-dist.test
index 91e30c546..fe7582b42 100644
--- a/tests/Composer/Test/Fixtures/installer/install-dev-using-dist.test
+++ b/tests/Composer/Test/Fixtures/installer/install-dev-using-dist.test
@@ -41,7 +41,7 @@ install --prefer-dist
             "type": "library"
         }
     ],
-    "packages-dev": null,
+    "packages-dev": [],
     "aliases": [],
     "minimum-stability": "dev",
     "stability-flags": {
diff --git a/tests/Composer/Test/Fixtures/installer/update-alias-lock.test b/tests/Composer/Test/Fixtures/installer/update-alias-lock.test
index 46ce63b75..ad9451c6f 100644
--- a/tests/Composer/Test/Fixtures/installer/update-alias-lock.test
+++ b/tests/Composer/Test/Fixtures/installer/update-alias-lock.test
@@ -60,7 +60,7 @@ update
             "type": "library"
         }
     ],
-    "packages-dev": null,
+    "packages-dev": [],
     "aliases": [],
     "minimum-stability": "dev",
     "stability-flags": [],
diff --git a/tests/Composer/Test/Fixtures/installer/updating-dev-updates-url-and-reference.test b/tests/Composer/Test/Fixtures/installer/updating-dev-updates-url-and-reference.test
index ee92652e6..3eb701719 100644
--- a/tests/Composer/Test/Fixtures/installer/updating-dev-updates-url-and-reference.test
+++ b/tests/Composer/Test/Fixtures/installer/updating-dev-updates-url-and-reference.test
@@ -53,7 +53,7 @@ update
             "dist": { "reference": "newref", "url": "newurl", "type": "zip", "shasum": "" }
         }
     ],
-    "packages-dev": null,
+    "packages-dev": [],
     "aliases": [],
     "minimum-stability": "dev",
     "stability-flags": {"a/a":20},