How to solve the complex differential

Dear all

I want to calculate the differential of 'f' defined below.

When I get ‘df1’， I want to caculate df1(eta ,v ,v0, kappa, lambda ,rho ,r ,q ,t ,0).

but subs(df1,'x',0) doesn't work!!!

 Error using mupadmex
Error in MuPAD command: Division by zero. [_power]

Evaluating: symobj::trysubs

Error in sym/subs>mupadsubs (line 146) G = mupadmex('symobj::fullsubs',F.s,X2,Y2);

Error in sym/subs (line 119) G = mupadsubs(F,X,Y);

How can I deal with it? Thanks in advance:) ================================================================================================ syms eta v v0 kappa lambda rho r q t x

d=sqrt((rho*lambda*x*1i)^2-lambda^2*(-x*1i-x^2)); g=(kappa-rho*lambda*x*1i)/(kappa-rho*lambda*x*1i+d);

f=exp(x*(r-q)*t*1i)*exp(eta*kappa*lambda^(-2)*((kappa-rho*lambda*x*1i-d)*t-2*log((1-g*exp(-d*t))/(1-g))))... exp(v0*lambda^(-2)(kappa-rho*lambda*x*1i-d)*(1-exp(-d*t))/(1-g*exp(-d*t)));

df1=diff(f,'x',1); =================================================================================================