diff --git a/Lib/gftools/builder/operations/autohintOTF.py b/Lib/gftools/builder/operations/autohintOTF.py
index aa6443f1..0fdca4ec 100644
--- a/Lib/gftools/builder/operations/autohintOTF.py
+++ b/Lib/gftools/builder/operations/autohintOTF.py
@@ -3,4 +3,4 @@
 
 class AutohintOTF(OperationBase):
     description = "Run otfautohint"
-    rule = "otfautohint $args -o $out $in \|\| otfautohint $args -o $out $in --no-zones-stems"
+    rule = r"otfautohint $args -o $out $in \|\| otfautohint $args -o $out $in --no-zones-stems"