Cum invocarem te exaudisti me

Folio: 
039r
Sequence: 
6
Office/Mass: 
MI
Genre: 
Cm
Cantus ID: 
g00697
Mode: 
2
Finalis: 
D
Manuscript Reading Full Text (standardized spelling): 
Cum invocarem te exaudisti me Deus justitiae meae in tribulatione dilatasti me miserere mihi Domine et exaudi orationem meam
Manuscript Reading Full Text (MS spelling): 
Cum invocarem te exaudisti me deus justitiae mee in tribulatione dilatasti me miserere mei domine et exaudi orationem meam.
Indexing notes: 
Looks like "mei" in manuscript, not "mihi" (6th word from the end), is this a scribal error perhaps?