diff --git a/lib/xcodeproj/constants.rb b/lib/xcodeproj/constants.rb
index 083d47d8..543a7b2f 100644
--- a/lib/xcodeproj/constants.rb
+++ b/lib/xcodeproj/constants.rb
@@ -36,7 +36,7 @@ module Constants
 
     # @return [String] The last known object version to Xcodeproj.
     #
-    LAST_KNOWN_OBJECT_VERSION = 60
+    LAST_KNOWN_OBJECT_VERSION = 63
 
     # @return [String] The last known Xcode version to Xcodeproj.
     #
@@ -132,6 +132,7 @@ module Constants
     # @return [Hash] The compatibility version string for different object versions.
     #
     COMPATIBILITY_VERSION_BY_OBJECT_VERSION = {
+      63 => 'Xcode 15.3',
       60 => 'Xcode 15.0',
       56 => 'Xcode 14.0',
       55 => 'Xcode 13.0',
diff --git a/lib/xcodeproj/project/object/root_object.rb b/lib/xcodeproj/project/object/root_object.rb
index 26b8a741..8737400f 100644
--- a/lib/xcodeproj/project/object/root_object.rb
+++ b/lib/xcodeproj/project/object/root_object.rb
@@ -49,6 +49,10 @@ class PBXProject < AbstractObject
         #
         has_one :main_group, PBXGroup
 
+        #  @return [String] whether minimizes project reference proxies
+        #
+        attribute :minimized_project_reference_proxies, String, '0'
+
         # @return [PBXGroup] the group containing the references to products of
         #         the project.
         #
diff --git a/spec/project/object/root_object_spec.rb b/spec/project/object/root_object_spec.rb
index 282e41a7..45493fda 100644
--- a/spec/project/object/root_object_spec.rb
+++ b/spec/project/object/root_object_spec.rb
@@ -39,6 +39,10 @@ module ProjectSpecs
       @root_object.main_group.class.should == PBXGroup
     end
 
+    it 'returns whether the project minimized project reference proxies' do
+      @root_object.minimized_project_reference_proxies.should == '0'
+    end
+
     it 'returns the products group' do
       @root_object.product_ref_group.class.should == PBXGroup
     end