diff --git a/src/cryptography/hazmat/bindings/openssl/x509.py b/src/cryptography/hazmat/bindings/openssl/x509.py
index b5c9ee1..fd7a12a 100644
--- a/src/cryptography/hazmat/bindings/openssl/x509.py
+++ b/src/cryptography/hazmat/bindings/openssl/x509.py
@@ -140,6 +140,7 @@
 
 int X509_get_ext_count(X509 *);
 int X509_add_ext(X509 *, X509_EXTENSION *, int);
+X509_EXTENSION *X509_delete_ext(X509 *, int);
 X509_EXTENSION *X509_EXTENSION_dup(X509_EXTENSION *);
 X509_EXTENSION *X509_get_ext(X509 *, int);
 int X509_get_ext_by_NID(X509 *, int, int);