Hi, I ran into a problem with STON that seems to corrupt on materialization. Consider the following script: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ c := OrderedCollection with: UUID new. d := Dictionary with: c first -> nil. o := { c . d }. s := STON toStringPretty: o. o2 := STON reader allowComplexMapKeys: true; on: s readStream; next. o2 second keys. "an Array(an UUID('571bbfb7-78b9-430c-9aad-3e0088a25f4c'))" o2 second printString. "KeyNotFound: key an UUID(''571bbfb7-78b9-430c-9aad-3e0088a25f4c'') not found in Dictionary" o2 second at: o2 second keys first. "the same error" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ So even though it contains the key it fails to access it. Interestingly enough if I serialize and materialize the "broken" dictionary again it suddenly works again. Thanks, Peter