diff --git a/.travis.yml b/.travis.yml
index d8dd167..15dfb03 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -5,6 +5,8 @@ rvm:
   - 2.1.0
   - 2.2.0
   - 2.3.0
+  - 2.4.0
+  - ruby-head
   - jruby-head
   - rbx-2
 
diff --git a/test/common.rb b/test/common.rb
index 4a26cdc..f4d28d1 100644
--- a/test/common.rb
+++ b/test/common.rb
@@ -70,7 +70,7 @@ def assert_progress_reported_put(offset, data, expect={})
 
     def assert_progress_reported_get(offset, data, expect={})
       assert_equal offset, current_event[3] if offset
-      if data.is_a?(Fixnum)
+      if data.is_a?(0.class)
         assert_equal data, current_event[4].length
       elsif data
         assert_equal data, current_event[4]