Comparative's lack of agreement?

I could use some help on this puzzle I am experiencing:

In the following sentence, why is the adjective "δεινότερον" in the neuter when it seems to be modifying a feminine noun, "προδοσία"? I'm clearly missing something and I don't know what :(

καίτοι τοσούτῳ μὲν δεινότερον προδοσία πολέμου, ὅσῳ χαλεπώτερον φυλάξασθαι τὸ ἀφανὲς τοῦ φανεροῦ

Please help me understand!