pet not leveling ( ragnaros )

Today i tamed a new pet ( winterspring frostsaber ), after taming it i took it to level in forlorn woods. ( by the way i am a level 80 hunter )
the first 10 minutes it gained 0 xp, after that it got xp but slowly, i managed to get my pet to level 78 after 30 minutes of killing mobs.
after that it gained xp pretty fast, but when i killed the last mob my pet got that leveling sound and that yellow glow for a second as an indicator that it leveled up, so ilooked and my pet was still level 78, after killing mobs for 30 minutes my pet leveled 3 times and every time that it leveled it was still level 78... anybody else had this problem?

Thnx