diff --git a/lib/parallel.rb b/lib/parallel.rb
index 612602b4..9b6077bd 100644
--- a/lib/parallel.rb
+++ b/lib/parallel.rb
@@ -232,6 +232,7 @@ def each_with_index(array, options={}, &block)
     end
 
     def map(source, options = {}, &block)
+      options = options.dup
       options[:mutex] = Mutex.new
 
       if options[:in_processes] && options[:in_threads]
diff --git a/spec/parallel_spec.rb b/spec/parallel_spec.rb
index cd6e2b1f..c722278a 100644
--- a/spec/parallel_spec.rb
+++ b/spec/parallel_spec.rb
@@ -225,6 +225,10 @@ def cpus
       }.should <= 3.5
     end
 
+    it "does not modify options" do
+      lambda { Parallel.map([], {}.freeze) }.should_not raise_error
+    end
+
     it "executes with given parameters" do
       `ruby spec/cases/parallel_map.rb`.should == "-a- -b- -c- -d-"
     end
@@ -233,7 +237,7 @@ def cpus
       `ruby spec/cases/parallel_map_complex_objects.rb`.should == "YES"
     end
 
-    it "starts new process imediatly when old exists" do
+    it "starts new process immediately when old exists" do
       time_taken{
       `ruby spec/cases/parallel_map_uneven.rb`
       }.should <= 3.5