diff --git a/lib/simplecov/lines_classifier.rb b/lib/simplecov/lines_classifier.rb
index c86311c3..41026840 100644
--- a/lib/simplecov/lines_classifier.rb
+++ b/lib/simplecov/lines_classifier.rb
@@ -8,8 +8,8 @@ class LinesClassifier
     RELEVANT = 0
     NOT_RELEVANT = nil
 
-    WHITESPACE_LINE = /^\s*$/
-    COMMENT_LINE = /^\s*#/
+    WHITESPACE_LINE = /^\s*$/.freeze
+    COMMENT_LINE = /^\s*#/.freeze
     WHITESPACE_OR_COMMENT_LINE = Regexp.union(WHITESPACE_LINE, COMMENT_LINE)
 
     def self.no_cov_line
diff --git a/lib/simplecov/source_file.rb b/lib/simplecov/source_file.rb
index 43fbfba6..3d9efcd6 100644
--- a/lib/simplecov/source_file.rb
+++ b/lib/simplecov/source_file.rb
@@ -190,7 +190,7 @@ def load_source
       end
     end
 
-    SHEBANG_REGEX = /\A#!/
+    SHEBANG_REGEX = /\A#!/.freeze
     def shebang?(line)
       SHEBANG_REGEX.match?(line)
     end
@@ -202,7 +202,7 @@ def read_lines(file, lines, current_line)
       lines.concat([current_line], ensure_remove_undefs(file.readlines))
     end
 
-    RUBY_FILE_ENCODING_MAGIC_COMMENT_REGEX = /\A#\s*(?:-\*-)?\s*(?:en)?coding:\s*(\S+)\s*(?:-\*-)?\s*\z/
+    RUBY_FILE_ENCODING_MAGIC_COMMENT_REGEX = /\A#\s*(?:-\*-)?\s*(?:en)?coding:\s*(\S+)\s*(?:-\*-)?\s*\z/.freeze
     def set_encoding_based_on_magic_comment(file, line)
       # Check for encoding magic comment
       # Encoding magic comment must be placed at first line except for shebang