diff --git a/spec/prawn_manual_spec.rb b/spec/prawn_manual_spec.rb
index 46b39e7a1..e85c39b5d 100644
--- a/spec/prawn_manual_spec.rb
+++ b/spec/prawn_manual_spec.rb
@@ -15,7 +15,7 @@
   describe 'manual' do
     # JRuby's zlib is a bit quirky. It sometimes produces different output to
     # libzlib (used by MRI). It's still a proper deflate stream and can be
-    # decompressed just fine, but for whatever reason, compression produces
+    # decompressed just fine but, for whatever reason, compression produces
     # different output.
     #
     # See: https://github.com/jruby/jruby/issues/4244