diff --git a/lib/respect/schema.rb b/lib/respect/schema.rb
index <HASH>..<HASH> 100644
--- a/lib/respect/schema.rb
+++ b/lib/respect/schema.rb
@@ -215,9 +215,9 @@ module Respect
       valid
     end
 
-    # Sanitize the given +doc+ if it validates this schema. The sanitized document
+    # Sanitize the given +doc+ *in-place* if it validates this schema. The sanitized document
     # is returned. {ValidationError} is raised on error.
-    def sanitize(doc)
+    def sanitize!(doc)
       validate(doc)
       sanitize_doc!(doc, sanitized_doc)
     end
diff --git a/test/schema_test.rb b/test/schema_test.rb
index <HASH>..<HASH> 100644
--- a/test/schema_test.rb
+++ b/test/schema_test.rb
@@ -145,10 +145,10 @@ class SchemaTest < Test::Unit::TestCase
     s = Respect::Schema.define do |s|
       s.boolean
     end
-    assert_equal false, s.sanitize(false)
-    assert_equal true, s.sanitize(true)
+    assert_equal false, s.sanitize!(false)
+    assert_equal true, s.sanitize!(true)
     assert_raise(Respect::ValidationError) do
-      s.sanitize(nil)
+      s.sanitize!(nil)
     end
   end
Rename Schema#sanitize to Schema#sanitize!.

Make it clear there are side-effects.