diff --git a/railties/lib/rails/backtrace_cleaner.rb b/railties/lib/rails/backtrace_cleaner.rb
index 7c2eb1dc42..6ac963e1ef 100644
--- a/railties/lib/rails/backtrace_cleaner.rb
+++ b/railties/lib/rails/backtrace_cleaner.rb
@@ -4,18 +4,25 @@ require "active_support/backtrace_cleaner"
 
 module Rails
   class BacktraceCleaner < ActiveSupport::BacktraceCleaner
-    APP_DIRS_PATTERN = /^\/?(app|config|lib|test|\(\w*\))/
+    APP_DIRS_PATTERN = /\A\/?(?:app|config|lib|test|\(\w*\))/
     RENDER_TEMPLATE_PATTERN = /:in `.*_\w+_{2,3}\d+_\d+'/
-    EMPTY_STRING = ""
-    SLASH        = "/"
-    DOT_SLASH    = "./"
 
     def initialize
       super
       @root = "#{Rails.root}/"
-      add_filter { |line| line.sub(@root, EMPTY_STRING) }
-      add_filter { |line| line.sub(RENDER_TEMPLATE_PATTERN, EMPTY_STRING) }
-      add_filter { |line| line.sub(DOT_SLASH, SLASH) } # for tests
+      add_filter do |line|
+        line.start_with?(@root) ? line.from(@root.size) : line
+      end
+      add_filter do |line|
+        if RENDER_TEMPLATE_PATTERN.match?(line)
+          line.sub(RENDER_TEMPLATE_PATTERN, "")
+        else
+          line
+        end
+      end
+      add_filter do |line|
+        line.start_with?("./") ? line.from(1) : line
+      end
       add_silencer { |line| !APP_DIRS_PATTERN.match?(line) }
     end
   end