diff --git a/include/mbedtls/ctr_drbg.h b/include/mbedtls/ctr_drbg.h
index c91ca58..cc3df7b 100644
--- a/include/mbedtls/ctr_drbg.h
+++ b/include/mbedtls/ctr_drbg.h
@@ -36,6 +36,12 @@
 #ifndef MBEDTLS_CTR_DRBG_H
 #define MBEDTLS_CTR_DRBG_H
 
+#if !defined(MBEDTLS_CONFIG_FILE)
+#include "config.h"
+#else
+#include MBEDTLS_CONFIG_FILE
+#endif
+
 #include "aes.h"
 
 #if defined(MBEDTLS_THREADING_C)
@@ -239,18 +245,20 @@
 /**
  * \brief              This function updates the state of the CTR_DRBG context.
  *
- * \note               If \p add_len is greater than
- *                     #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT, only the first
- *                     #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT Bytes are used.
- *                     The remaining Bytes are silently discarded.
- *
  * \param ctx          The CTR_DRBG context.
  * \param additional   The data to update the state with.
- * \param add_len      Length of \p additional data.
+ * \param add_len      Length of \p additional in bytes. This must be at
+ *                     most #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT.
  *
+ * \return             \c 0 on success.
+ * \return             #MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG if
+ *                     \p add_len is more than
+ *                     #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT.
+ * \return             An error from the underlying AES cipher on failure.
  */
-void mbedtls_ctr_drbg_update( mbedtls_ctr_drbg_context *ctx,
-                      const unsigned char *additional, size_t add_len );
+int mbedtls_ctr_drbg_update_ret( mbedtls_ctr_drbg_context *ctx,
+                                 const unsigned char *additional,
+                                 size_t add_len );
 
 /**
  * \brief   This function updates a CTR_DRBG instance with additional
@@ -290,6 +298,35 @@
 int mbedtls_ctr_drbg_random( void *p_rng,
                      unsigned char *output, size_t output_len );
 
+
+#if ! defined(MBEDTLS_DEPRECATED_REMOVED)
+#if defined(MBEDTLS_DEPRECATED_WARNING)
+#define MBEDTLS_DEPRECATED    __attribute__((deprecated))
+#else
+#define MBEDTLS_DEPRECATED
+#endif
+/**
+ * \brief              This function updates the state of the CTR_DRBG context.
+ *
+ * \deprecated         Superseded by mbedtls_ctr_drbg_update_ret()
+ *                     in 2.16.0.
+ *
+ * \note               If \p add_len is greater than
+ *                     #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT, only the first
+ *                     #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT Bytes are used.
+ *                     The remaining Bytes are silently discarded.
+ *
+ * \param ctx          The CTR_DRBG context.
+ * \param additional   The data to update the state with.
+ * \param add_len      Length of \p additional data.
+ */
+MBEDTLS_DEPRECATED void mbedtls_ctr_drbg_update(
+    mbedtls_ctr_drbg_context *ctx,
+    const unsigned char *additional,
+    size_t add_len );
+#undef MBEDTLS_DEPRECATED
+#endif /* !MBEDTLS_DEPRECATED_REMOVED */
+
 #if defined(MBEDTLS_FS_IO)
 /**
  * \brief               This function writes a seed file.
@@ -319,6 +356,8 @@
 int mbedtls_ctr_drbg_update_seed_file( mbedtls_ctr_drbg_context *ctx, const char *path );
 #endif /* MBEDTLS_FS_IO */
 
+#if defined(MBEDTLS_SELF_TEST)
+
 /**
  * \brief               The CTR_DRBG checkup routine.
  *
@@ -327,6 +366,8 @@
  */
 int mbedtls_ctr_drbg_self_test( int verbose );
 
+#endif /* MBEDTLS_SELF_TEST */
+
 /* Internal functions (do not call directly) */
 int mbedtls_ctr_drbg_seed_entropy_len( mbedtls_ctr_drbg_context *,
                                int (*)(void *, unsigned char *, size_t), void *,