diff --git a/tools/format_test.txt b/tools/format_test.txt
new file mode 100644
index 0000000..9306d90
--- /dev/null
+++ b/tools/format_test.txt
@@ -0,0 +1,5 @@
+Nor
+\uUnderline\u\u
+\bBold\b
+\k\k\k\k\k\k   mal
+\j\j\j\j
diff --git a/tools/printfile.py b/tools/printfile.py
index cfe42ca..a2883d5 100644
--- a/tools/printfile.py
+++ b/tools/printfile.py
@@ -47,7 +47,7 @@ def main():
     lines=[x.rstrip() for x in lines] # remove whitespaces and linebreaks
     
     for iline,line in enumerate(lines):
-        if not set(line).issubset(chars):
+        if not set(line).issubset(chars+'\\'): 
             print(str(iline)+":"+str(line))
             print("Contains non printable characters")
             exit()