diff --git a/powerwall.sh b/powerwall.sh
index bd1f1bbf..295c531a 100755
--- a/powerwall.sh
+++ b/powerwall.sh
@@ -52,8 +52,8 @@ CHECKTEMP_SERVICE(){
 				echo ${TEMP_THRESHOLDS[${1}]} | cut -d',' -f 1 | read temp_warn
 				echo ${TEMP_THRESHOLDS[${1}]} | cut -d',' -f 2 | read temp_crit
 				
-				temp_diff=$((last_temp%.* - temp_f%.*))
-				[ $temp_diff -lt 0 ] && temp_diff=$((temp_diff * -1))
+				temp_diff=$(($last_temp%.* - $temp_f%.*))
+				[ $temp_diff -lt 0 ] && temp_diff=$(($temp_diff * -1))
 						
 				if [ $(bc -l <<< "$temp_f >= $temp_warn") -eq 1 ] && [ $(bc -l <<< "$temp_f < $temp_crit") -eq 1 ]; then
 					if [ [ $temp_diff -gt 1 ] || [ "$last_temp" == "0" ] ]; then