diff --git a/src/args.jl b/src/args.jl
index d582af9c..8faded96 100644
--- a/src/args.jl
+++ b/src/args.jl
@@ -1276,7 +1276,8 @@ end
 
 # -----------------------------------------------------------------------------
 
-has_black_border_for_default(st) = error("The seriestype attribute only accepts Symbols, you passed $st.")
+has_black_border_for_default(st) = error("The seriestype attribute only accepts Symbols, you passed the $(typeof(st)) $st.")
+has_black_border_for_default(st::Function) = error("The seriestype attribute only accepts Symbols, you passed the function $st.")
 function has_black_border_for_default(st::Symbol)
     like_histogram(st) || st in (:hexbin, :bar, :shape)
 end