diff --git a/library/psa_crypto_cipher.c b/library/psa_crypto_cipher.c
index 09bd28c..ae30e5f 100644
--- a/library/psa_crypto_cipher.c
+++ b/library/psa_crypto_cipher.c
@@ -449,6 +449,8 @@
     const uint8_t *key_buffer,
     size_t key_buffer_size,
     psa_algorithm_t alg,
+    const uint8_t *iv,
+    size_t iv_length,
     const uint8_t *input,
     size_t input_length,
     uint8_t *output,
@@ -457,7 +459,7 @@
 {
     psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;
     mbedtls_psa_cipher_operation_t operation = MBEDTLS_PSA_CIPHER_OPERATION_INIT;
-    size_t olength, accumulated_length;
+    size_t update_output_length, finish_output_length;
 
     status = mbedtls_psa_cipher_encrypt_setup( &operation, attributes,
                                                key_buffer, key_buffer_size,
@@ -465,33 +467,27 @@
     if( status != PSA_SUCCESS )
         goto exit;
 
-    accumulated_length = 0;
-    if( operation.iv_length > 0 )
+    if( iv_length > 0 )
     {
-        status = mbedtls_psa_cipher_set_iv( &operation,
-                                            output, operation.iv_length );
+        status = mbedtls_psa_cipher_set_iv( &operation, iv, iv_length );
         if( status != PSA_SUCCESS )
             goto exit;
-
-        accumulated_length = operation.iv_length;
     }
 
     status = mbedtls_psa_cipher_update( &operation, input, input_length,
-                                        output + operation.iv_length,
-                                        output_size - operation.iv_length,
-                                        &olength );
+                                        output, output_size,
+                                        &update_output_length );
     if( status != PSA_SUCCESS )
         goto exit;
 
-    accumulated_length += olength;
-
-    status = mbedtls_psa_cipher_finish( &operation, output + accumulated_length,
-                                        output_size - accumulated_length,
-                                        &olength );
+    status = mbedtls_psa_cipher_finish( &operation,
+                                        output + update_output_length,
+                                        output_size - update_output_length,
+                                        &finish_output_length );
     if( status != PSA_SUCCESS )
         goto exit;
 
-    *output_length = accumulated_length + olength;
+    *output_length = update_output_length + finish_output_length;
 
 exit:
     if( status == PSA_SUCCESS )