diff --git a/crypto/pool/internal.h b/crypto/pool/internal.h
new file mode 100644
index 0000000..3ec2ec2
--- /dev/null
+++ b/crypto/pool/internal.h
@@ -0,0 +1,45 @@
+/* Copyright (c) 2016, Google Inc.
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
+ * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
+ * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
+ * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
+
+#ifndef OPENSSL_HEADER_POOL_INTERNAL_H
+#define OPENSSL_HEADER_POOL_INTERNAL_H
+
+#include <openssl/lhash.h>
+#include <openssl/thread.h>
+
+#if defined(__cplusplus)
+extern "C" {
+#endif
+
+
+DECLARE_LHASH_OF(CRYPTO_BUFFER);
+
+struct crypto_buffer_st {
+  CRYPTO_BUFFER_POOL *pool;
+  uint8_t *data;
+  size_t len;
+  CRYPTO_refcount_t references;
+};
+
+struct crypto_buffer_pool_st {
+  LHASH_OF(CRYPTO_BUFFER) *bufs;
+  CRYPTO_MUTEX lock;
+};
+
+
+#if defined(__cplusplus)
+} /* extern C */
+#endif
+
+#endif /* OPENSSL_HEADER_POOL_INTERNAL_H */