diff --git a/ChangeLog.d/psa_cipher_update_ecp.txt b/ChangeLog.d/psa_cipher_update_ecp.txt
new file mode 100644
index 000000000..1c3fbc6b1
--- /dev/null
+++ b/ChangeLog.d/psa_cipher_update_ecp.txt
@@ -0,0 +1,2 @@
+Bugfix
+   * Fix a parameter set but unused in psa_crypto_cipher.c. Fixes #4935.
diff --git a/library/psa_crypto_cipher.c b/library/psa_crypto_cipher.c
index f67b1ffed..5c78c2311 100644
--- a/library/psa_crypto_cipher.c
+++ b/library/psa_crypto_cipher.c
@@ -268,9 +268,8 @@ static psa_status_t cipher_set_iv( mbedtls_psa_cipher_operation_t *operation,
  *                      This does not need to be aligned to a block boundary.
  *                      If there is a partial block at the end of the input,
  *                      it is stored in \p ctx for future processing.
- * \param output        The buffer where the output is written.
- * \param output_size   The size of \p output in bytes.
- *                      It must be at least `floor((p + input_length) / BS)`
+ * \param output        The buffer where the output is written. Its size
+ *                      must be at least `floor((p + input_length) / BS)`
  *                      where `p` is the number of bytes in the unprocessed
  *                      partial block in \p ctx (`0 <= p <= BS - 1`) and
  *                      `BS` is the block size.
@@ -284,7 +283,6 @@ static psa_status_t psa_cipher_update_ecb(
     const uint8_t *input,
     size_t input_length,
     uint8_t *output,
-    size_t output_size,
     size_t *output_length )
 {
     psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;
@@ -324,7 +322,6 @@ static psa_status_t psa_cipher_update_ecb(
                 goto exit;
 
             output += internal_output_length;
-            output_size -= internal_output_length;
             *output_length += internal_output_length;
             ctx->unprocessed_len = 0;
         }
@@ -345,7 +342,6 @@ static psa_status_t psa_cipher_update_ecb(
         input += block_size;
 
         output += internal_output_length;
-        output_size -= internal_output_length;
         *output_length += internal_output_length;
     }
 
@@ -400,7 +396,6 @@ static psa_status_t cipher_update( mbedtls_psa_cipher_operation_t *operation,
                                         input,
                                         input_length,
                                         output,
-                                        output_size,
                                         output_length );
     }
     else