diff --git a/src/Composer/Package/AliasPackage.php b/src/Composer/Package/AliasPackage.php
index 6c7d4dd02..5c2645eb1 100644
--- a/src/Composer/Package/AliasPackage.php
+++ b/src/Composer/Package/AliasPackage.php
@@ -75,7 +75,7 @@ class AliasPackage extends BasePackage
     /**
      * @return BasePackage
      */
-    public function getAliasOf(): BasePackage
+    public function getAliasOf()
     {
         return $this->aliasOf;
     }
diff --git a/src/Composer/Package/CompleteAliasPackage.php b/src/Composer/Package/CompleteAliasPackage.php
index 99bf51198..ea2dfad45 100644
--- a/src/Composer/Package/CompleteAliasPackage.php
+++ b/src/Composer/Package/CompleteAliasPackage.php
@@ -35,7 +35,7 @@ class CompleteAliasPackage extends AliasPackage implements CompletePackageInterf
     /**
      * @return CompletePackage
      */
-    public function getAliasOf(): CompletePackage
+    public function getAliasOf()
     {
         return $this->aliasOf;
     }
diff --git a/src/Composer/Package/RootAliasPackage.php b/src/Composer/Package/RootAliasPackage.php
index 807ec3b82..adf69b6b0 100644
--- a/src/Composer/Package/RootAliasPackage.php
+++ b/src/Composer/Package/RootAliasPackage.php
@@ -35,7 +35,7 @@ class RootAliasPackage extends CompleteAliasPackage implements RootPackageInterf
     /**
      * @return RootPackage
      */
-    public function getAliasOf(): RootPackage
+    public function getAliasOf()
     {
         return $this->aliasOf;
     }