diff --git a/src/backends/gr.jl b/src/backends/gr.jl
index d9f041b2..f4bdcd4d 100644
--- a/src/backends/gr.jl
+++ b/src/backends/gr.jl
@@ -741,9 +741,9 @@ function gr_get_ticks_size(ticks, rot)
     return w, h
 end
 
-gr_tick_label(axis,label) = (axis[:formatter] in (:scientific, :auto)) ?
-                                gr_convert_sci_tick_label(label) :
-                                label
+gr_tick_label(axis, label) =
+    (axis[:formatter] in (:scientific, :auto)) ? gr_convert_sci_tick_label(string(label)) :
+    string(label)
 
 function gr_convert_sci_tick_label(label)
     caret_split = split(label,'^')