Property reactivity issue with Named Consequence

When "if" construct is involved, property reactivity is not properly calculated. For example, the following rule results in an infinite loop even though 'oldPrice' is not used in LHS.

rule R1 when
    $a: Cheese ( type == "stilton" )
    if ( price > 10 ) break[t1]
then
    modify( $a ) { setOldPrice(10) };
then[t1]
    modify( $a ) { setOldPrice(15) };
end