diff --git a/schemars_derive/src/regex_syntax.rs b/schemars_derive/src/regex_syntax.rs
index 353bf8d..750d1e2 100644
--- a/schemars_derive/src/regex_syntax.rs
+++ b/schemars_derive/src/regex_syntax.rs
@@ -1,5 +1,31 @@
 // Copied from regex_syntax crate to avoid pulling in the whole crate just for a utility function
 // https://github.com/rust-lang/regex/blob/ff283badce21dcebd581909d38b81f2c8c9bfb54/regex-syntax/src/lib.rs
+//
+// Copyright (c) 2014 The Rust Project Developers
+//
+// Permission is hereby granted, free of charge, to any
+// person obtaining a copy of this software and associated
+// documentation files (the "Software"), to deal in the
+// Software without restriction, including without
+// limitation the rights to use, copy, modify, merge,
+// publish, distribute, sublicense, and/or sell copies of
+// the Software, and to permit persons to whom the Software
+// is furnished to do so, subject to the following
+// conditions:
+//
+// The above copyright notice and this permission notice
+// shall be included in all copies or substantial portions
+// of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
+// ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+// TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+// PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
+// SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+// CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
+// IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
 
 pub fn escape(text: &str) -> String {
     let mut quoted = String::new();