Water is a key volatile that provides insights into the initial stages of planet formation. However, little is known about the water vapor abundance in newly formed planet-forming disks. We present H_2_^18^O line observations with ALMA and NOEMA millimeter interferometers toward five young stellar objects. NOEMA observed the 203GHz line while ALMA targeted the 390GHz line. No emission is detected toward any of our five Class I disks. We report upper limits to the integrated line intensities. The inferred water column densities in Class I disks are <10^15^cm^-2^ on 100au scales which include both disk and envelope. Water vapor is not abundant in warm protostellar envelopes around Class I protostars. Upper limits to the water vapor column densities in Class I disks are at least two orders magnitude lower than values found in Class 0 disk-like structures.

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