diff --git a/library/psa_crypto_cipher.c b/library/psa_crypto_cipher.c
index ed43085..4d5bf20 100644
--- a/library/psa_crypto_cipher.c
+++ b/library/psa_crypto_cipher.c
@@ -532,6 +532,12 @@
     if( status != PSA_SUCCESS )
         goto exit;
 
+    if( output_size < accumulated_length )
+    {
+        status = PSA_ERROR_BUFFER_TOO_SMALL;
+        goto exit;
+    }
+
     status = cipher_finish( &operation, output + accumulated_length,
                             output_size - accumulated_length, &olength );
     accumulated_length += olength;