diff --git a/lib/6to5/transformation/transformers/_block-hoist.js b/lib/6to5/transformation/transformers/_block-hoist.js
index b6fff4a860..e024a8a193 100644
--- a/lib/6to5/transformation/transformers/_block-hoist.js
+++ b/lib/6to5/transformation/transformers/_block-hoist.js
@@ -1,4 +1,5 @@
-var _ = require("lodash");
+var useStrict = require("./use-strict");
+var _         = require("lodash");
 
 // Priority:
 //
@@ -17,13 +18,15 @@ exports.Program = {
     }
     if (!hasChange) return;
 
-    var nodePriorities = _.groupBy(node.body, function (bodyNode) {
-      var priority = bodyNode._blockHoist;
-      if (priority == null) priority = 1;
-      if (priority === true) priority = 2;
-      return priority;
-    });
+    useStrict._wrap(node, function () {
+      var nodePriorities = _.groupBy(node.body, function (bodyNode) {
+        var priority = bodyNode._blockHoist;
+        if (priority == null) priority = 1;
+        if (priority === true) priority = 2;
+        return priority;
+      });
 
-    node.body = _.flatten(_.values(nodePriorities).reverse());
+      node.body = _.flatten(_.values(nodePriorities).reverse());
+    });
   }
 };
diff --git a/lib/6to5/transformation/transformers/_declarations.js b/lib/6to5/transformation/transformers/_declarations.js
index ae0f355b08..20fbfadb6e 100644
--- a/lib/6to5/transformation/transformers/_declarations.js
+++ b/lib/6to5/transformation/transformers/_declarations.js
@@ -1,4 +1,5 @@
-var t = require("../../types");
+var useStrict = require("./use-strict");
+var t         = require("../../types");
 
 exports.secondPass = true;
 
@@ -7,23 +8,25 @@ exports.Program = function (node) {
   var kinds = {};
   var kind;
 
-  for (var i in node._declarations) {
-    var declar = node._declarations[i];
+  useStrict._wrap(node, function () {
+    for (var i in node._declarations) {
+      var declar = node._declarations[i];
 
-    kind = declar.kind || "var";
-    var declarNode = t.variableDeclarator(declar.id, declar.init);
+      kind = declar.kind || "var";
+      var declarNode = t.variableDeclarator(declar.id, declar.init);
 
-    if (!declar.init) {
-      kinds[kind] = kinds[kind] || [];
-      kinds[kind].push(declarNode);
-    } else {
-      node.body.unshift(t.variableDeclaration(kind, [declarNode]));
+      if (!declar.init) {
+        kinds[kind] = kinds[kind] || [];
+        kinds[kind].push(declarNode);
+      } else {
+        node.body.unshift(t.variableDeclaration(kind, [declarNode]));
+      }
     }
-  }
 
-  for (kind in kinds) {
-    node.body.unshift(t.variableDeclaration(kind, kinds[kind]));
-  }
+    for (kind in kinds) {
+      node.body.unshift(t.variableDeclaration(kind, kinds[kind]));
+    }
+  });
 
   node._declarations = null;
 };
diff --git a/lib/6to5/transformation/transformers/use-strict.js b/lib/6to5/transformation/transformers/use-strict.js
index 02d4dbc264..bd9fd9c651 100644
--- a/lib/6to5/transformation/transformers/use-strict.js
+++ b/lib/6to5/transformation/transformers/use-strict.js
@@ -1,14 +1,27 @@
 var t = require("../../types");
 
+exports._has = function (node) {
+  var first = node.body[0];
+  return t.isExpressionStatement(first) && t.isLiteral(first.expression, { value: "use strict" });
+};
+
+exports._wrap = function (node, callback) {
+  var useStrictNode;
+  if (exports._has(node)) {
+    useStrictNode = node.body.shift();
+  }
+
+  callback();
+
+  if (useStrictNode) {
+    node.body.unshift(useStrictNode);
+  }
+};
+
 exports.ast = {
   exit: function (ast) {
-    var body = ast.program.body;
-    var first = body[0];
-
-    var noStrict = !first || !t.isExpressionStatement(first) || !t.isLiteral(first.expression) || first.expression.value !== "use strict";
-
-    if (noStrict) {
-      body.unshift(t.expressionStatement(t.literal("use strict")));
+    if (!exports._has(ast.program)) {
+      ast.program.body.unshift(t.expressionStatement(t.literal("use strict")));
     }
   }
 };