diff --git a/src/os400qc3.c b/src/os400qc3.c
index 64d4df06b0..f60b850a59 100644
--- a/src/os400qc3.c
+++ b/src/os400qc3.c
@@ -956,6 +956,8 @@ null_token(const char *token)
 void
 _libssh2_os400qc3_crypto_dtor(_libssh2_os400qc3_crypto_ctx *x)
 {
+    if (!x)
+        return;
     if (!null_token(x->hash.Alg_Context_Token)) {
         Qc3DestroyAlgorithmContext(x->hash.Alg_Context_Token, (char *) &ecnull);
         memset(x->hash.Alg_Context_Token, 0, sizeof x->hash.Alg_Context_Token);
@@ -964,6 +966,11 @@ _libssh2_os400qc3_crypto_dtor(_libssh2_os400qc3_crypto_ctx *x)
         Qc3DestroyKeyContext(x->key.Key_Context_Token, (char *) &ecnull);
         memset(x->key.Key_Context_Token, 0, sizeof x->key.Key_Context_Token);
     }
+    if (x->kek) {
+        _libssh2_os400qc3_crypto_dtor(x->kek);
+        free((char *) x->kek);
+        x->kek = NULL;
+    }
 }
 
 /*******************************************************************
diff --git a/src/os400qc3.h b/src/os400qc3.h
index daca943f46..784b3ad493 100644
--- a/src/os400qc3.h
+++ b/src/os400qc3.h
@@ -189,10 +189,13 @@
  *
  *******************************************************************/
 
-typedef struct {        /* HMAC & private key algorithms support structure. */
-    Qc3_Format_ALGD0100_T   hash;           /* Hash algorithm. */
-    Qc3_Format_KEYD0100_T   key;            /* Key. */
-}       _libssh2_os400qc3_crypto_ctx;
+/* HMAC & private key algorithms support structure. */
+typedef struct _libssh2_os400qc3_crypto_ctx _libssh2_os400qc3_crypto_ctx;
+struct _libssh2_os400qc3_crypto_ctx {
+    Qc3_Format_ALGD0100_T           hash;           /* Hash algorithm. */
+    Qc3_Format_KEYD0100_T           key;            /* Key. */
+    _libssh2_os400qc3_crypto_ctx *  kek;            /* Key encryption. */
+};
 
 typedef struct {        /* Big number. */
     unsigned char *         bignum;         /* Number bits, little-endian. */
@@ -240,7 +243,9 @@ typedef struct {        /* Algorithm description. */
                                 libssh2_os400qc3_hash_update(&(ctx), data, len)
 #define libssh2_md5_final(ctx, out)                                         \
                                 libssh2_os400qc3_hash_final(&(ctx), out)
-#define libssh2_hmac_ctx_init(ctx)
+#define libssh2_hmac_ctx_init(ctx)                                          \
+                                memset((char *) &(ctx), 0,                  \
+                                       sizeof(libssh2_hmac_ctx))
 #define libssh2_hmac_md5_init(ctx, key, keylen)                             \
                                 libssh2_os400qc3_hmac_init(ctx, Qc3_MD5,    \
                                                            key, keylen)