diff --git a/index.bs b/index.bs
index 9bea8d26..f93e6bd4 100644
--- a/index.bs
+++ b/index.bs
@@ -2010,7 +2010,7 @@ Parsers SHALL ignore these two fields.
 class IAConfigurationBox extends Box('iacb') {
     unsigned int (8) configurationVersion = 1;
     leb128() configOBUs_size;
-    unsigned int (8) configOBUs[];
+    unsigned int (8 x configOBUs_size) configOBUs;
 }
 ```