diff --git a/include/mbedtls/gcm.h b/include/mbedtls/gcm.h
index 98faa43612..837ec1f59a 100644
--- a/include/mbedtls/gcm.h
+++ b/include/mbedtls/gcm.h
@@ -115,10 +115,9 @@ int mbedtls_gcm_setkey(mbedtls_gcm_context *ctx,
 /**
  * \brief           This function performs GCM encryption or decryption of a buffer.
  *
- * \note            For encryption, the output buffer can be the same as the
- *                  input buffer. For decryption, the output buffer cannot be
- *                  the same as input buffer. If the buffers overlap, the output
- *                  buffer must trail at least 8 Bytes behind the input buffer.
+ * \note            The output buffer \p output can be the same as the input
+ *                  buffer \p input. If \p output is greater than \p input, they
+ *                  cannot overlap.
  *
  * \warning         When this function performs a decryption, it outputs the
  *                  authentication tag and does not verify that the data is
@@ -287,9 +286,11 @@ int mbedtls_gcm_update_ad(mbedtls_gcm_context *ctx,
  *                    to this function during an operation, then it is
  *                    correct to use \p output_size = \p input_length.
  *
- * \note            For decryption, the output buffer cannot be the same as
- *                  input buffer. If the buffers overlap, the output buffer
- *                  must trail at least 8 Bytes behind the input buffer.
+ * \note            The output buffer \p output can be the same as the input
+ *                  buffer \p input. If \p output is greater than \p input, they
+ *                  cannot overlap. Implementations which require
+ *                  MBEDTLS_GCM_ALT to be enabled may not provide support for
+ *                  overlapping buffers.
  *
  * \param ctx           The GCM context. This must be initialized.
  * \param input         The buffer holding the input data. If \p input_length