Volley Vs. Sleep

You make some noise as you are attacked. Teranoth utters the words, 'grzzs'. You manage to reflect Teranoth's spell back at him! Teranoth's legs buckle, and he suddenly slumps to the ground and sleeps. You dodge Teranoth's attack. Volleyed a sleep back to him, but the fight was still initiated, I'm assuming because he didn't sleep me the attack still went through, but is it meant this way or just something overlooked?