diff --git a/.rspec b/.rspec
new file mode 100644
index 0000000..372b5ac
--- /dev/null
+++ b/.rspec
@@ -0,0 +1 @@
+--warnings
diff --git a/lib/simplecov_json_formatter/source_file_formatter.rb b/lib/simplecov_json_formatter/source_file_formatter.rb
index 3564c79..6f44f52 100644
--- a/lib/simplecov_json_formatter/source_file_formatter.rb
+++ b/lib/simplecov_json_formatter/source_file_formatter.rb
@@ -4,6 +4,7 @@ module SimpleCovJSONFormatter
   class SourceFileFormatter
     def initialize(source_file)
       @source_file = source_file
+      @line_coverage = nil
     end
 
     def format
@@ -17,7 +18,7 @@ def format
     private
 
     def line_coverage
-      @line_coverage || {
+      @line_coverage ||= {
         lines: lines
       }
     end