diff --git a/src/_cffi_src/openssl/x509.py b/src/_cffi_src/openssl/x509.py
index 112f4ed..4cdc827 100644
--- a/src/_cffi_src/openssl/x509.py
+++ b/src/_cffi_src/openssl/x509.py
@@ -36,7 +36,13 @@
     ...;
 } X509_CINF;
 
-typedef ... X509_EXTENSION;
+/* TODO: opaque X509_EXTENSION. Cryptography no longer depends on it being
+   non-opaque but pyOpenSSL needs a release where it doesn't depend on this */
+typedef struct {
+    ASN1_OBJECT *object;
+    ASN1_BOOLEAN critical;
+    ASN1_OCTET_STRING *value;
+} X509_EXTENSION;
 
 typedef ... X509_EXTENSIONS;
 typedef ... X509_REQ_INFO;