diff --git a/etc/kaleidoscope-builder.conf b/etc/kaleidoscope-builder.conf
index da7b3b12..490fc4b3 100644
--- a/etc/kaleidoscope-builder.conf
+++ b/etc/kaleidoscope-builder.conf
@@ -3,7 +3,7 @@
 ## NEEDS: SKETCH
 ## Should be included when the current directory is the dir of the Sketch.
 
-SKETCH="${SKETCH:-${DEFAULT_SKETCH}}"
+: "${SKETCH:=${DEFAULT_SKETCH}}"
 
 ########
 ######## Keyboard hardware definitions