diff --git a/import-layers/yocto-poky/meta/classes/logging.bbclass b/import-layers/yocto-poky/meta/classes/logging.bbclass
index 06c7c31..a0c94e9 100644
--- a/import-layers/yocto-poky/meta/classes/logging.bbclass
+++ b/import-layers/yocto-poky/meta/classes/logging.bbclass
@@ -86,7 +86,7 @@
 	
 	# Strip off the debug level and ensure it is an integer
 	DBGLVL=$1; shift
-	NONDIGITS=$(echo "$DBGLVL" | tr -d [:digit:])
+	NONDIGITS=$(echo "$DBGLVL" | tr -d "[:digit:]")
 	if [ "$NONDIGITS" ]; then
 		bbfatal "$USAGE"
 	fi