Previous analyses of the effect of vowel elision on tone in Yoruba have been largely confined to the Standard dialect (Pulleyblank 1986, Akinlabi and Liberman 2001). The Moba dialect differs from the Standard in one tonal environment: where the two tones of the hiatus vowels are high and low sequentially, the non-elided vowel surfaces with a high tone in Standard Yoruba, and a mid tone in Moba Yoruba. This paper uses the concept of tone feature geometries (Bao 1999, Snider 1999) to provide an autosegmental analysis of elision in this tonal environment, suggesting that the mid tone resulting in the Moba dialect arises out of tonal fusion between the high and low tones of the elided and non-elided hiatus vowels.