MATLAB: Double ticks in right axis plotyy

MATLABticks tickmarkersplotyy

On the right axis there's the tickmarks of the left axis visible. This is the code:
subplot( 3,2,2 )
[ AxesH1, hh1, hh2 ] = plotyy( frequency, fftrr, frequency, fftabscd);
set(AxesH1(1),'YLim',[ 0 ynewrr ]);
set(AxesH1(2),'YLim',[ 0 ynewcd ]);
line( Fmarkrr, Pmarkrr, 'linestyle', 'none', 'Marker', '*', 'Parent', AxesH1(1));
line( Fmarkcd, Pmarkcd, 'linestyle', 'none', 'Marker', '*', 'Parent', AxesH1(2));
xlabel( 'Frequentie (Hz)' )
title( 'HRV & MCD' )
ylabel( 'SP (a.u.)' )
hold off
What piece of my code could be causing this?