diff --git a/library/chacha20_internal.h b/library/chacha20_internal.h
new file mode 100644
index 0000000000..7b2a062a99
--- /dev/null
+++ b/library/chacha20_internal.h
@@ -0,0 +1,21 @@
+/**
+ * \file chacha20_internal.h
+ *
+ * \brief Internal declarations for ChaCha20.
+ */
+/*
+ *  Copyright The Mbed TLS Contributors
+ *  SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
+ */
+
+#ifndef MBEDTLS_CHACHA20_INTERNAL_H
+#define MBEDTLS_CHACHA20_INTERNAL_H
+
+#include "common.h"
+
+#include "mbedtls/chacha20.h"
+
+int mbedtls_chacha20_check_counter_wrap(const mbedtls_chacha20_context *ctx,
+                                        size_t size);
+
+#endif /* MBEDTLS_CHACHA20_INTERNAL_H */