diff --git a/strings.sol b/strings.sol
index 0a2d68bd..7f2d0ef4 100644
--- a/strings.sol
+++ b/strings.sol
@@ -1,3 +1,4 @@
+pragma solidity ^0.4.11;
 /*
  * @title String & slice utility library for Solidity contracts.
  * @author Nick Johnson <arachnid@notdot.net>
diff --git a/strings_test.sol b/strings_test.sol
index efd182c7..9c0903ba 100644
--- a/strings_test.sol
+++ b/strings_test.sol
@@ -1,3 +1,4 @@
+pragma solidity ^0.4.11;
 import 'dapple/test.sol';
 import 'strings.sol';