diff --git a/library/psa_crypto.c b/library/psa_crypto.c
index 1609c74..9cccf53 100644
--- a/library/psa_crypto.c
+++ b/library/psa_crypto.c
@@ -19,6 +19,7 @@
  */
 
 #include "common.h"
+#include "psa_crypto_core_common.h"
 
 #if defined(MBEDTLS_PSA_CRYPTO_C)
 
@@ -4226,7 +4227,7 @@
     status = psa_driver_wrapper_cipher_encrypt(
         &attributes, slot->key.data, slot->key.bytes,
         alg, local_iv, default_iv_length, input, input_length,
-        mbedtls_buffer_offset(output, default_iv_length),
+        psa_crypto_buffer_offset(output, default_iv_length),
         output_size - default_iv_length, output_length);
 
 exit:
diff --git a/library/psa_crypto_core_common.h b/library/psa_crypto_core_common.h
new file mode 100644
index 0000000..dd72ab1
--- /dev/null
+++ b/library/psa_crypto_core_common.h
@@ -0,0 +1,64 @@
+/**
+ * \file psa_crypto_core_common.h
+ *
+ * \brief Utility macros for internal use in the PSA cryptography core.
+ */
+/*
+ *  Copyright The Mbed TLS Contributors
+ *  SPDX-License-Identifier: Apache-2.0
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License"); you may
+ *  not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+
+#ifndef PSA_CRYPTO_CORE_COMMON_H
+#define PSA_CRYPTO_CORE_COMMON_H
+
+/** Return an offset into a buffer.
+ *
+ * This is just the addition of an offset to a pointer, except that this
+ * function also accepts an offset of 0 into a buffer whose pointer is null.
+ * (`p + n` has undefined behavior when `p` is null, even when `n == 0`.
+ * A null pointer is a valid buffer pointer when the size is 0, for example
+ * as the result of `malloc(0)` on some platforms.)
+ *
+ * \param p     Pointer to a buffer of at least n bytes.
+ *              This may be \p NULL if \p n is zero.
+ * \param n     An offset in bytes.
+ * \return      Pointer to offset \p n in the buffer \p p.
+ *              Note that this is only a valid pointer if the size of the
+ *              buffer is at least \p n + 1.
+ */
+static inline unsigned char *psa_crypto_buffer_offset(
+    unsigned char *p, size_t n)
+{
+    return p == NULL ? NULL : p + n;
+}
+
+/** Return an offset into a read-only buffer.
+ *
+ * Similar to mbedtls_buffer_offset(), but for const pointers.
+ *
+ * \param p     Pointer to a buffer of at least n bytes.
+ *              This may be \p NULL if \p n is zero.
+ * \param n     An offset in bytes.
+ * \return      Pointer to offset \p n in the buffer \p p.
+ *              Note that this is only a valid pointer if the size of the
+ *              buffer is at least \p n + 1.
+ */
+static inline const unsigned char *psa_crypto_buffer_offset_const(
+    const unsigned char *p, size_t n)
+{
+    return p == NULL ? NULL : p + n;
+}
+
+#endif /* PSA_CRYPTO_CORE_COMMON_H */