Problem with "globalsolve:true"



Hi,

Does anybody understand why K2 in the following script is not solved global?
What am I doing wrong? In my opinion the last line should be:
M(z)=z*A-(q*z^2)/2

(%i1) M(z)::=K2+A*z-q*z^2/2;
(%o1) M(z)::=K2+A*z+((-q)*z^2)/2

(%i2) globalsolve:true$

(%i3) solve([M(z)=0,z=0],[K2,z]);
(%o3) [[K2=0,z=0]]

(%i4) display(M(z))$

M(z)=K2+z*A-(q*z^2)/2