Some research on written production has focused on the role of the syllable as a processing unit. However, the precise nature of this syllable unit has yet to be elucidated. The present study examined whether the nature of this processing unit is orthographic (i.e., an ortho-syllable) or phonological. We asked French adults to copy three-syllable and two-syllable words with or without a mute e. In French, a silent e may affect the orthographic syllabification of a word and increase the number of ortho-syllables. In Experiment 1, the mute e was in final position. The presence of the mute e increased writing latencies. In Experiment 2, which compared words with or without an internal mute e, the latencies for three-syllable words did not differ from those for two-syllable words containing a mute e. These results support the hypothesis that handwriting has a specific orthographic processing unit based on graphemic constituents.