diff --git a/lib/ruby-metrics/agent.rb b/lib/ruby-metrics/agent.rb
index 168cee3..dc88856 100644
--- a/lib/ruby-metrics/agent.rb
+++ b/lib/ruby-metrics/agent.rb
@@ -43,7 +43,7 @@ def timer(name, units = "", options = {})
     end
 
     def uniform_histogram(name, units = "")
-      @instruments[name] ||= Instruments::UniformHistogram.new(:units => units)
+      @instruments[name] ||= Instruments::UniformHistogram.new
     end
 
     # For backwards compatibility