diff --git a/openssl/src/crypto.rs b/openssl/src/crypto.rs
index 16698b40..519135cc 100644
--- a/openssl/src/crypto.rs
+++ b/openssl/src/crypto.rs
@@ -1,4 +1,5 @@
 #![doc(hidden)]
+#![deprecated(since = "0.9.20")]
 use string::OpensslString;
 
 #[deprecated(note = "renamed to OpensslString", since = "0.9.7")]