Adoro Te Devote

Has anyone else noticed a discrepancy in the hymn "Adoro Te Devote" in different editions of the first verse of the Latin?
I believe the discrepancy lies with how many times we sing the solfegge "sol." What I mean is, do we solfegge: do-mi-so-so-so-so-la-so to the words "A-do-ro-te-de-vo-o-te" OR we solfegge do-mi-so-so-so-la-so to the words "A-do-ro-te-de-vo-te." See the difference? Do we slur the note belonging to the sixth syllable (which is what all of the other English and Latin verses do,) or do we have an extra "sol" that none of the other versions or verses have?
I had never thought much about this, except that this semester I am learning Langlais' Elevation (on Adoro Te Devote) from Suite Medieval. When I first looked at it with my teacher, he casually commented how Langlais had apparently made a mistake and "put an extra note in." That triggered my memory of briefly wondering about this. I just checked the St. Pius X hymnal, and the first verse simply has an extra "sol" note which none of the other verses use.

All that being said, I think my whole point is simply that Langlais was not wrong. While he probably didn't use the Pius X hymnal, he certainly knew the hymn. He didn't write an extra note, it actually is there, just in the first verse of the Latin! :-)