diff --git a/lib/rubygems/resolver/api_specification.rb b/lib/rubygems/resolver/api_specification.rb
index a47d910331..232c2b041b 100644
--- a/lib/rubygems/resolver/api_specification.rb
+++ b/lib/rubygems/resolver/api_specification.rb
@@ -6,6 +6,17 @@
 # is the name, version, and dependencies.
 
 class Gem::Resolver::APISpecification < Gem::Resolver::Specification
+  ##
+  # We assume that all instances of this class are immutable;
+  # so avoid duplicated generation for performance.
+  @@cache = {}
+  def self.new(set, api_data)
+    cache_key = [set, api_data]
+    cache = @@cache[cache_key]
+    return cache if cache
+    @@cache[cache_key] = super
+  end
+
   ##
   # Creates an APISpecification for the given +set+ from the rubygems.org
   # +api_data+.
@@ -18,12 +29,12 @@ class Gem::Resolver::APISpecification < Gem::Resolver::Specification
 
     @set = set
     @name = api_data[:name]
-    @version = Gem::Version.new api_data[:number]
-    @platform = Gem::Platform.new api_data[:platform]
-    @original_platform = api_data[:platform]
+    @version = Gem::Version.new(api_data[:number]).freeze
+    @platform = Gem::Platform.new(api_data[:platform]).freeze
+    @original_platform = api_data[:platform].freeze
     @dependencies = api_data[:dependencies].map do |name, ver|
-      Gem::Dependency.new name, ver.split(/\s*,\s*/)
-    end
+      Gem::Dependency.new(name, ver.split(/\s*,\s*/)).freeze
+    end.freeze
   end
 
   def ==(other) # :nodoc: