diff --git a/lib/krb5/krb5.h b/lib/krb5/krb5.h
index 220701037..a4e266631 100644
--- a/lib/krb5/krb5.h
+++ b/lib/krb5/krb5.h
@@ -760,6 +760,28 @@ struct credentials; /* this is to keep the compiler happy */
 struct getargs;
 struct sockaddr;
 
+/**
+ * Semi private, not stable yet
+ */
+
+typedef struct krb5_crypto_iov {
+    unsigned int flags;
+    /* ignored */
+#define KRB5_CRYPTO_TYPE_EMPTY		0
+    /* OUT krb5_crypto_length(crypto, len, KRB5_CRYPTO_TYPE_HEADER) */
+#define KRB5_CRYPTO_TYPE_HEADER		1
+    /* IN and OUT */
+#define KRB5_CRYPTO_TYPE_DATA		2
+    /* IN */
+#define KRB5_CRYPTO_TYPE_SIGN_ONLY	3
+   /* (only for encryption) OUT krb5_crypto_length(crypto, len, KRB5_CRYPTO_TYPE_TRAILER) */
+#define KRB5_CRYPTO_TYPE_PADDING	4
+   /* OUT krb5_crypto_length(crypto, len, KRB5_CRYPTO_TYPE_TRAILER) */
+#define KRB5_CRYPTO_TYPE_TRAILER	5
+    krb5_data data;
+} krb5_crypto_iov;
+
+
 #include <krb5-protos.h>
 
 /* variables */