A pronunciation issue? For me, the H in mihi sounds like the voiceless velar fricative x (as x in Greek and Slavic languages or ch in German), while the h should be the sound similar to the German h (glottal fricative).
A slightly rasped, velar sound is probably not entirely off. In medieval Latin it was often written as michi, which shows that the h sound in the word had developed into a k sound. It probably passed through a velar fricative stage on its way there.