diff --git a/include/mbedtls/ctr_drbg.h b/include/mbedtls/ctr_drbg.h
index e554a0aff..2b4dc73d3 100644
--- a/include/mbedtls/ctr_drbg.h
+++ b/include/mbedtls/ctr_drbg.h
@@ -227,14 +227,37 @@ int mbedtls_ctr_drbg_reseed( mbedtls_ctr_drbg_context *ctx,
  *
  * \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.
  *
- * \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.
+ * \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.
+ */
+int mbedtls_ctr_drbg_update_ret( mbedtls_ctr_drbg_context *ctx,
+                                 const unsigned char *additional,
+                                 size_t add_len );
+
+/**
+ * \brief               This function updates the state of the CTR_DRBG context.
+ *
+ * \warning             This function cannot report errors. You should use
+ *                      mbedtls_ctr_drbg_update_ret() instead.
+ *
+ * \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.
  */
 void mbedtls_ctr_drbg_update( mbedtls_ctr_drbg_context *ctx,
-                      const unsigned char *additional, size_t add_len );
+                              const unsigned char *additional,
+                              size_t add_len );
 
 /**
  * \brief   This function updates a CTR_DRBG instance with additional
diff --git a/library/ctr_drbg.c b/library/ctr_drbg.c
index fc3188eb3..d7a94840c 100644
--- a/library/ctr_drbg.c
+++ b/library/ctr_drbg.c
@@ -303,22 +303,36 @@ exit:
     return( ret );
 }
 
-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 )
 {
     unsigned char add_input[MBEDTLS_CTR_DRBG_SEEDLEN];
+    int ret;
 
-    if( add_len > 0 )
-    {
-        /* MAX_INPUT would be more logical here, but we have to match
-         * block_cipher_df()'s limits since we can't propagate errors */
-        if( add_len > MBEDTLS_CTR_DRBG_MAX_SEED_INPUT )
-            add_len = MBEDTLS_CTR_DRBG_MAX_SEED_INPUT;
+    if( add_len == 0 )
+        return( 0 );
 
-        block_cipher_df( add_input, additional, add_len );
-        ctr_drbg_update_internal( ctx, add_input );
-        mbedtls_zeroize( add_input, sizeof( add_input ) );
-    }
+    if( ( ret = block_cipher_df( add_input, additional, add_len ) ) != 0 )
+        goto exit;
+    if( ( ret = ctr_drbg_update_internal( ctx, add_input ) ) != 0 )
+        goto exit;
+
+exit:
+    mbedtls_zeroize( add_input, sizeof( add_input ) );
+    return( ret );
+}
+
+/* Deprecated function, kept for backward compatibility. */
+void mbedtls_ctr_drbg_update( mbedtls_ctr_drbg_context *ctx,
+                              const unsigned char *additional,
+                              size_t add_len )
+{
+    /* MAX_INPUT would be more logical here, but we have to match
+     * block_cipher_df()'s limits since we can't propagate errors */
+    if( add_len > MBEDTLS_CTR_DRBG_MAX_SEED_INPUT )
+        add_len = MBEDTLS_CTR_DRBG_MAX_SEED_INPUT;
+    (void) mbedtls_ctr_drbg_update_ret( ctx, additional, add_len );
 }
 
 int mbedtls_ctr_drbg_reseed( mbedtls_ctr_drbg_context *ctx,
@@ -514,7 +528,7 @@ int mbedtls_ctr_drbg_update_seed_file( mbedtls_ctr_drbg_context *ctx, const char
     if( fread( buf, 1, n, f ) != n )
         ret = MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR;
     else
-        mbedtls_ctr_drbg_update( ctx, buf, n );
+        ret = mbedtls_ctr_drbg_update_ret( ctx, buf, n );
 
     fclose( f );
 
diff --git a/tests/suites/test_suite_ctr_drbg.function b/tests/suites/test_suite_ctr_drbg.function
index d8ffebe46..f17bd3be0 100644
--- a/tests/suites/test_suite_ctr_drbg.function
+++ b/tests/suites/test_suite_ctr_drbg.function
@@ -177,9 +177,11 @@ void ctr_drbg_entropy_usage( )
     }
     TEST_ASSERT( last_idx == test_offset_idx );
 
-    /* Call update with too much data (sizeof entropy > MAX(_SEED)_INPUT)
-     * (just make sure it doesn't cause memory corruption) */
-    mbedtls_ctr_drbg_update( &ctx, entropy, sizeof( entropy ) );
+    /* Call update with too much data (sizeof entropy > MAX(_SEED)_INPUT).
+     * Make sure it's detected as an error and doesn't cause memory
+     * corruption. */
+    TEST_ASSERT( mbedtls_ctr_drbg_update_ret(
+                     &ctx, entropy, sizeof( entropy ) ) != 0 );
 
     /* Now enable PR, so the next few calls should all reseed */
     mbedtls_ctr_drbg_set_prediction_resistance( &ctx, MBEDTLS_CTR_DRBG_PR_ON );