Fix for systems without EC
diff --git a/cryptography/hazmat/bindings/openssl/ec.py b/cryptography/hazmat/bindings/openssl/ec.py
index c0c4f88..c3ca6e9 100644
--- a/cryptography/hazmat/bindings/openssl/ec.py
+++ b/cryptography/hazmat/bindings/openssl/ec.py
@@ -23,10 +23,7 @@
 static const int Cryptography_HAS_EC;
 
 typedef ... EC_KEY;
-typedef struct {
-    int nid;
-    const char *comment;
-} EC_builtin_curve;
+typedef ... EC_builtin_curve;
 
 static const int NID_X9_62_prime192v1;
 static const int NID_X9_62_prime192v2;
@@ -45,6 +42,8 @@
 void EC_KEY_free(EC_KEY *);
 
 size_t EC_get_builtin_curves(EC_builtin_curve *, size_t);
+
+int Cryptography_EC_builtin_curve_get_nid(EC_builtin_curve);
 """
 
 CUSTOMIZATIONS = """
@@ -55,8 +54,13 @@
 EC_KEY* (*EC_KEY_new_by_curve_name)(int) = NULL;
 void (*EC_KEY_free)(EC_KEY *) = NULL;
 size_t (*EC_get_builtin_curves)(EC_builtin_curve *, size_t) = NULL;
+int (*Cryptography_EC_builtin_curve_get_nid)(EC_builtin_curve) = NULL;
 #else
 static const long Cryptography_HAS_EC = 1;
+
+int Cryptography_EC_builtin_curve_get_nid(EC_builtin_curve c) {
+    return c.nid;
+}
 #endif
 """
 
@@ -64,5 +68,8 @@
     "Cryptography_HAS_EC": [
         "EC_KEY_new_by_curve_name",
         "EC_KEY_free",
+        "EC_get_builtin_curves",
+
+        "Cryptography_EC_builtin_curve_get_nid",
     ],
 }