Avoiding extension attack

I am considering the following "addition" to the Preneel-Miyaguchi hash
scheme
to avoid the "extension attack" (calculating the hash of M || M'
without knowing M,
but only the hash of M) :

H_0 = 0
H_i = E(H_i-1, M_i) + H_i-1 + M_i (i = 1 .. m)
H_m+1 = E(0, H_m + L) + H_m + L

where
   a) M = M_1 || M_2 || .... || M_m is an L-bit message, and M_i are
blocks
   b) M_m is right padded with zeros if necessary
   c) + is xor
   e) E(K, X) is the encryption function
   f) H_m+1 is the hash of M

You see any flaw ?
This was tried before ? Any links ?

Thanks

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Alexis Machado