diff --git a/cryptography/bindings/openssl/hmac.py b/cryptography/bindings/openssl/hmac.py
index 7a9d05b..e97ac35 100644
--- a/cryptography/bindings/openssl/hmac.py
+++ b/cryptography/bindings/openssl/hmac.py
@@ -16,8 +16,7 @@
 """
 
 TYPES = """
-struct hmac_ctx_st { ...; };
-typedef struct hmac_ctx_st HMAC_CTX;
+typedef struct { ...; } HMAC_CTX;
 """
 
 FUNCTIONS = """