diff --git a/lib/youplot/backends/processing.rb b/lib/youplot/backends/processing.rb
index 9b7bcb2..5ce6a8f 100644
--- a/lib/youplot/backends/processing.rb
+++ b/lib/youplot/backends/processing.rb
@@ -6,9 +6,9 @@ module YouPlot
     module Processing
       module_function
 
-      def count_values(arr)
+      def count_values(arr, tally: true)
         # tally was added in Ruby 2.7
-        if Enumerable.method_defined? :tally
+        if tally && Enumerable.method_defined?(:tally)
           arr.tally
         else
           # https://github.com/marcandre/backports
diff --git a/test/youplot/backends/processing_test.rb b/test/youplot/backends/processing_test.rb
index 94275f8..88954b5 100644
--- a/test/youplot/backends/processing_test.rb
+++ b/test/youplot/backends/processing_test.rb
@@ -8,4 +8,10 @@ class YouPlotCommandTest < Test::Unit::TestCase
     assert_equal([%i[a b c], [3, 2, 1]], @m.count_values(%i[a a a b b c]))
     assert_equal([%i[c b a], [3, 2, 1]], @m.count_values(%i[a b b c c c]))
   end
+
+  test :count_values_non_tally do
+    @m = YouPlot::Backends::Processing
+    assert_equal([%i[a b c], [3, 2, 1]], @m.count_values(%i[a a a b b c], tally: false))
+    assert_equal([%i[c b a], [3, 2, 1]], @m.count_values(%i[a b b c c c], tally: false))
+  end
 end