Errors converting from single complex to mp complex and back

I'm getting errors when I try to convert a single-precision complex variable to mp type and back. For example:
>> x = single(1 + i)
x =
1.0000 + 1.0000i
>> x = mp(x)
x =
6.94449606095542138733663817572487e-310 + 5.263544247120890312873936353273975e-315i

Due to the nature of the application I'm working on, I can't get around this by using a string, e.g. mp('1+i'); I have to convert from a single-precision variable. Presently I'm getting around this by casting the variable to double before passing it to mp, e.g. x = mp(double(x)), but I'd like to not have to do that.

In addition, when I try to cast from mp to single, the variable gets cast to a double instead. For example:
>> x = mp('1+i')
x =
1 + 1i
>> x = single(x)
x =
1.0000 + 1.0000i
>> whos
Name Size Bytes Class Attributes
x 1x1 16 double complex

Presently I'm getting around this issue by calling single() twice, e.g. x = single(single(x)), but again, I'd like to not have to do that.

I'm using MATLAB version 8.4.0.150421 (R2014b) and mp version 3.8.5 Build 9059.