diff --git a/vignettes/overview.Rmd b/vignettes/overview.Rmd
index af6c337..4bc4042 100644
--- a/vignettes/overview.Rmd
+++ b/vignettes/overview.Rmd
@@ -23,7 +23,6 @@ size_mod <- -5
 
 my_theme <- theme(plot.background=element_rect(fill = "transparent",
                                                colour = "transparent"),
-                  panel.grid.major = element_line(colour="grey", linetype = "dashed", size = 0.5),
                   panel.grid.major = element_line(colour="lightgrey", linetype = "dashed", size = 0.5),
                   panel.background = element_rect(fill = "transparent",colour = "black"),
                   legend.background = element_rect(fill = "NA"),