In ICC v4 colour management, data is exchanged between different colour encodings via a fixed Profile Connection Space (PCS), in which colorimetry is based on the D50 illuminant, and the CIE 1931 standard observer. According to the ICC specification, colorimetry that is based on a different illuminant, or observer should be transformed into the fixed PCS; however, while a chromatic adaptation method is specified for when illuminants are different, there is no method specified for differences in observer. The Waypoint method has been proposed as a means of transforming between different colorimetric data encodings. In this study a Waypoint-based method recommended by ICC was evaluated as a mechanism for transforming into the ICC PCS, as applied to a use case in digital textile printing in which source colorimetry is based on the D65 illuminant and the CIE 1964 observer. It was compared with an alternative approach in which a non-ICC PCS was used within a conventional ICC colour management framework. The results show that when both source and destination colorimetry are based on D65/10-degrees, both methods perform equally well. However, when the source and destination colorimetry do not match, the ICC approach of transforming via the standard PCS yields better results.