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Competitive methods for lossless screen content coding are based on modelling of probability distributions. The most effective approach for losslessly compressing images with up to 90000 colours is known as `soft context formation' (SCF). It scans the image to be compressed for repeating patterns and creates corresponding colour histograms. This yields excellent compression results as long as the actual pattern-based histogram contains the colour of the next pixel to be processed. If this colour is not contained, an exception handling is required by sending a special non-colour symbol (escape). This paper proposes an enhanced version of this exception handling coding. Instead of using an pattern-based estimation, the probability of the escape symbol is now modelled based on local dependencies of exception events leading to 1.4% decrease of bitrate. In comparison to FLIF, FP8v3, and HEVC (HM-16.20+SCM-8.8), the entire SCF method achieves savings of about 25%, 8%, and 11% on average for images with less than 90000 different colours (for 720p format).