diff --git a/lib/ice_cube/occurrence.rb b/lib/ice_cube/occurrence.rb
index 4c51f962..4cd849f5 100644
--- a/lib/ice_cube/occurrence.rb
+++ b/lib/ice_cube/occurrence.rb
@@ -86,7 +86,7 @@ def to_time
     #
     def to_s(format = nil)
       if format && to_time.public_method(:to_s).arity != 0
-        t0, t1 = start_time.to_s(format), end_time.to_s(format)
+        t0, t1 = start_time.to_formatted_s(format), end_time.to_formatted_s(format)
       else
         t0, t1 = start_time.to_s, end_time.to_s
       end
diff --git a/spec/examples/occurrence_spec.rb b/spec/examples/occurrence_spec.rb
index 80c18421..45f320ff 100644
--- a/spec/examples/occurrence_spec.rb
+++ b/spec/examples/occurrence_spec.rb
@@ -28,7 +28,7 @@
       time_now = Time.current
       occurrence = Occurrence.new(time_now)
 
-      expect(occurrence.to_s(:short)).to eq time_now.to_s(:short)
+      expect(occurrence.to_formatted_s(:short)).to eq time_now.to_formatted_s(:short)
     end
   end