diff --git a/tests/demo/draw/bug31908 b/tests/demo/draw/bug31908
index 217c5263ff..90db0917a2 100644
--- a/tests/demo/draw/bug31908
+++ b/tests/demo/draw/bug31908
@@ -4,5 +4,13 @@ puts "=========="
 puts ""
 pload MODELING 
 box b 10 20 30
-wavefront b the_name_of_saved_with_wavefront_command_box_that_measures_10_20_30_and_has_length_of_its_name_longer_than_100_characters
+
+# this test check use wavefront command with long file name
+set file_name "${imagedir}/${casename}"
+set path_length [string length $file_name]
+# but full path must be less than 255
+for {set i $path_length} {$i < 255} {incr i} {
+  append file_name "1"
+}
+wavefront b ${file_name}
 puts "TEST COMPLETED"