diff --git a/Library/Homebrew/dependencies.rb b/Library/Homebrew/dependencies.rb
index 3e8bd125e8..354b12745e 100644
--- a/Library/Homebrew/dependencies.rb
+++ b/Library/Homebrew/dependencies.rb
@@ -39,6 +39,11 @@ class Dependencies < SimpleDelegator
   def inspect
     "#<#{self.class.name}: #{__getobj__}>"
   end
+
+  sig { returns(T::Array[Dependency]) }
+  def to_a
+    __getobj__.to_a
+  end
 end
 
 # A collection of requirements.
diff --git a/Library/Homebrew/formula_cellar_checks.rb b/Library/Homebrew/formula_cellar_checks.rb
index 93cf4b9d7e..26e4f2f066 100644
--- a/Library/Homebrew/formula_cellar_checks.rb
+++ b/Library/Homebrew/formula_cellar_checks.rb
@@ -191,7 +191,7 @@ module FormulaCellarChecks
     EOS
   end
 
-  sig { params(lib: Pathname, deps: T::Array[Dependency]).returns(T.nilable(String)) }
+  sig { params(lib: Pathname, deps: Dependencies).returns(T.nilable(String)) }
   def check_python_packages(lib, deps)
     return unless lib.directory?
 
@@ -209,7 +209,8 @@ module FormulaCellarChecks
 
     return if pythons.blank?
 
-    python_deps = deps.map(&:name)
+    python_deps = deps.to_a
+                      .map(&:name)
                       .grep(/^python(@.*)?$/)
                       .filter_map { |d| Formula[d].version.to_s[/^\d+\.\d+/] }