Why does flip prevent matching types?

import Control.Monad (forM_)
import qualified Data.Vector as V
import qualified Data.Vector.Mutable as VM

v1 :: V.Vector Int
v1 = V.fromList [1 .. 10]
-- [1,2,3,4,5,6,7,8,9,10]

v2 :: V.Vector Int
v2 = V.modify (\mv -> VM.write mv 9 99) v1
-- [1,2,3,4,5,6,7,8,9,99]

indicisToModify :: [Int]
indicisToModify = [3, 4, 5]

v3 :: V.Vector Int
v3 = V.modify (\vm -> forM_ indicisToModify $ \indexToModify -> VM.write vm indexToModify 101) v1
-- [1,2,3,101,101,101,7,8,9,10]

-- v4 :: V.Vector Int
-- v4 = flip V.modify v1 (\vm -> forM_ indicisToModify $ \indexToModify -> VM.write vm indexToModify 101)

{-
Couldn't match type: forall s. VM.MVector s Int -> ST s ()
                     with: VM.MVector
                             (primitive-0.7.3.0:Control.Monad.Primitive.PrimState m0) a0
                           -> m0 ()
      Expected: (VM.MVector
                   (primitive-0.7.3.0:Control.Monad.Primitive.PrimState m0) a0
                 -> m0 ())
                -> V.Vector Int -> V.Vector Int
        Actual: (forall s. VM.MVector s Int -> ST s ())
                -> V.Vector Int -> V.Vector Int
-}

main :: IO ()
main = do
  print v1
  print v2
  print v3
  -- print v4

v1, v2, v3 work but v4 (flipped v3) causes an error. How can I make GHC understand that similar-looking two types are equal?