diff --git a/lib/command_duration.bash b/lib/command_duration.bash
index ffa6d5f1..aaccb48b 100644
--- a/lib/command_duration.bash
+++ b/lib/command_duration.bash
@@ -14,7 +14,7 @@ function _dynamic_clock_icon {
 	local clock_hand
 	# clock hand value is between 90 and 9b in hexadecimal.
 	# so between 144 and 155 in base 10.
-	clock_hand=$(printf '%x' $(((${1:-${SECONDS}} % 12) + 144)))
+	printf -v clock_hand '%x' $(( (${1:-${SECONDS}} % 12) + 144 ))
 	printf -v 'COMMAND_DURATION_ICON' '%b' "\xf0\x9f\x95\x$clock_hand"
 }