Rotating line in the legend in R in ggplot2

Question

Here is a simple example:

library(ggplot2)
library(data.table)

x<-data.table(y=rnorm(10),x=seq(1,10))
ggplot(x,aes(x=x,y=y))+geom_point()+geom_vline(aes(colour="a",xintercept=5))+
  scale_color_manual(name="",labels=c("My Line"),
                     values=c("a"="black"))

I would like line in the legend to be horizontal rather than vertical but have not managed to achieve that, maybe somebody has a suggestion.

I have a little bit hacky solution:

ggplot(x,aes(x=x,y=y))+geom_point()+geom_vline(aes(xintercept=5))+
  geom_hline(aes(colour="a",yintercept=Inf))+
  scale_color_manual(name="",labels=c("Super"),
                     values=c("a"="black"))+
  theme_bw()+
  theme(legend.position = "top")

Maybe somebody can propose something better.