diff --git a/dabo/functions/check_sell_conditions.sh b/dabo/functions/check_sell_conditions.sh
index 1d41c59..7af65e9 100644
--- a/dabo/functions/check_sell_conditions.sh
+++ b/dabo/functions/check_sell_conditions.sh
@@ -252,7 +252,7 @@ function check_sell_conditions_strategy {
 
 
   # check for SELL_PERCENTAGE_FROM_LAST_PURCHASE_NEGATIVE
-  if [ -z ${SELL_PERCENTAGE_FROM_LAST_PURCHASE_NEGATIVE} ]
+  if [ -n "${SELL_PERCENTAGE_FROM_LAST_PURCHASE_NEGATIVE}" ]
   then
     if [ $(echo "${f_BUY_PRICE_LAST_RATE_DIFF} < ${SELL_PERCENTAGE_FROM_LAST_PURCHASE_NEGATIVE}" | bc -l) -ne 0 ]
     then