AJ hand played passively

[Lunkan]

UTG+1 is very loose passive. Seen most flops and no preflop raises. (About 10 hands played with him when this hand took place)

Poker Room skin
Limit Holdem Ring game
Limit: $1/$2
9 players
Converter

Pre-flop: (9 players) wildhorses13 is Button with A[img]/images/graemlins/club.gif[/img] J[img]/images/graemlins/club.gif[/img]
UTG folds, UTG+1 calls, MP1 (poster) checks, MP2 calls, 2 folds, <font color="#cc0000">wildhorses13 raises</font>, 2 folds, UTG+1 calls, MP1 calls, MP2 calls.

Flop: Q[img]/images/graemlins/spade.gif[/img] K[img]/images/graemlins/diamond.gif[/img] 4[img]/images/graemlins/club.gif[/img] (9.5SB, 4 players)
UTG+1 checks, MP1 checks, MP2 checks, <font color="#cc0000">wildhorses13 bets</font>, UTG+1 calls, 2 folds.

Turn: A[img]/images/graemlins/diamond.gif[/img] (5.75BB, 2 players)
<font color="#cc0000">UTG+1 bets</font>, wildhorses13 calls.

River: 6[img]/images/graemlins/diamond.gif[/img] (7.75BB, 2 players)
<font color="#cc0000">UTG+1 bets</font>, wildhorses13 calls.

Results:
Final pot: 9.75BB

The donkbet from a passive player made me a bit scared and I decided to only call down from there. Too weak?