diff --git a/sandbox.lua b/sandbox.lua
index 1025a35..aec70d2 100644
--- a/sandbox.lua
+++ b/sandbox.lua
@@ -54,10 +54,12 @@ local function run(f, options)
   string.rep = nil
 
   setfenv(f, BASE_ENV)
-  local result = f()
+  local ok, result = pcall(f)
 
   string.rep = string_rep
 
+  if not ok then error(result) end
+
   return result
 end
 
diff --git a/spec/sandbox_spec.lua b/spec/sandbox_spec.lua
index 1461478..2e2dae8 100644
--- a/spec/sandbox_spec.lua
+++ b/spec/sandbox_spec.lua
@@ -33,6 +33,11 @@ describe('sandbox', function()
     assert.equal('hellohello', string.rep('hello', 2))
   end)
 
+  it('restores string.rep even if there is an error', function()
+    assert.has_error(function() sandbox("error('foo')") end)
+    assert.equal('hellohello', string.rep('hello', 2))
+  end)
+
 
 
 end)