Add ylab to ggplot with fivethirtyeight ggtheme

Is it possible to add a label to the y axis if you are using theme_fivethirtyeight? I tried ylab but it does not work:

library(ggplot2)
library(ggthemes)
p2 <- ggplot(mtcars, aes(x = wt, y = mpg, colour = factor(gear))) +
  geom_point() +
  ggtitle("Cars")
p2 + geom_smooth(method = "lm", se = FALSE) +
  scale_color_fivethirtyeight("cyl") +
  theme_fivethirtyeight() + ylab('SOMETHING')