diff --git a/lib/execjs/external_runtime.rb b/lib/execjs/external_runtime.rb
index 2f35cd6..78c517c 100644
--- a/lib/execjs/external_runtime.rb
+++ b/lib/execjs/external_runtime.rb
@@ -37,7 +37,9 @@ module ExecJS
 
         def compile(source)
           @runtime.send(:runner_source).dup.tap do |output|
-            output.sub!('#{source}', source)
+            output.sub!('#{source}') do
+              source
+            end
             output.sub!('#{json2_source}') do
               IO.read(ExecJS.root + "/support/json2.js")
             end
diff --git a/test/test_runtimes.rb b/test/test_runtimes.rb
index e45eccc..5d7d90c 100644
--- a/test/test_runtimes.rb
+++ b/test/test_runtimes.rb
@@ -14,6 +14,7 @@ module TestRuntime
     assert_equal "hello", @runtime.exec("return 'hello'")
     assert_equal({"a"=>1,"b"=>2}, @runtime.exec("return {a:1,b:2}"))
     assert_equal "café", @runtime.exec("return 'café'")
+    assert_equal "\\", @runtime.exec('return "\\\\"')
   end
 
   def test_eval
@@ -27,6 +28,7 @@ module TestRuntime
     assert_equal "hello", @runtime.eval("'hello'")
     assert_equal({"a"=>1,"b"=>2}, @runtime.eval("{a:1,b:2}"))
     assert_equal "café", @runtime.eval("'café'")
+    assert_equal "\\", @runtime.eval('"\\\\"')
   end
 
   def test_compile