# 460 Optimized Filters On NULL Values Not Working Properly

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I've found that filters for null values only work if there is no index on the field; e.g.:

Cost = NULL

successfully finds null values when there is no index on Cost, but when Cost is indexed the filter finds no matching records. It does, however, find non-null values, so

COST <> NULL

works, as does NOT (Cost <> Null).