Error message with geom_flag

[Bwe9403]

Hi there,

I've been trying to add flags to a bar plot using geom_flag. I've been using the following code:

countrytotal$COWcode <- countrycode(countrytotal$Fleet, "country.name", "cown")
countrytotal$countryname <- countrycode(countrytotal$COWcode, "cown", "country.name")
countrytotal$iso2 <- countrycode(countrytotal$countryname, "country.name", "iso2c")
countrytotal$iso2_lower <- tolower(countrytotal$iso2)

plot1 <- ggplot(data=countrytotal, aes(x=Fleet, y=totalcatch)) +
geom_bar(stat="identity") +
coord_flip() + expand_limits(y = -4)
plot1 + geom_flag(aes(y =-4, image = iso2_lower), data=countrytotal)

I continue to get the error message of Error in class(grobs) <- "gList" : attempt to set an attribute on NULL.

Any thoughts on what may be going on? Thank you.