error (109) "type mismatch" when using nlcom after reg3 (using aidsills)

Hello Statalisters,

I'm using aidsills command to estimate a QUAIDS model (which uses reg3 to estimate a non-linear system). The command works well, but when I try to construct elasticities using the stored parameters using nlcom I get the error 109 "type mismatch".

Has anyone faced a similar problem with reg3? I am using the data and examples from the main article "Estimating almost-ideal demand systems with endogenous regressors" (2015). Here is the code:

webuse food.dta
aidsills w1-w4 , pri(p1-p4) exp(expfd) qua

*Then, I try to test nlcom over the first parameter on e(b)
nlcom _b[w1:gamma_lnp1]

*This is the report

_nl_1: _b[w1:gamma_lnp1]
type mismatch
r(109)


Any ideas would be very helpful!