diff --git a/crypto/kdf/hkdf.c b/crypto/kdf/hkdf.c
index 6d1a32c885ecf..cab5e231fbe63 100644
--- a/crypto/kdf/hkdf.c
+++ b/crypto/kdf/hkdf.c
@@ -107,7 +107,10 @@ static int pkey_hkdf_ctrl(EVP_PKEY_CTX *ctx, int type, int p1, void *p2)
         if (kctx->key != NULL)
             OPENSSL_clear_free(kctx->key, kctx->key_len);
 
-        kctx->key = OPENSSL_memdup(p2, p1);
+        if (p1 == 0)
+            kctx->key = OPENSSL_zalloc(1);
+        else
+            kctx->key = OPENSSL_memdup(p2, p1);
         if (kctx->key == NULL)
             return 0;