diff --git a/dabo/functions/check_sell_conditions.sh b/dabo/functions/check_sell_conditions.sh
index f33e8a6..1d41c59 100644
--- a/dabo/functions/check_sell_conditions.sh
+++ b/dabo/functions/check_sell_conditions.sh
@@ -252,9 +252,12 @@ function check_sell_conditions_strategy {
 
 
   # check for SELL_PERCENTAGE_FROM_LAST_PURCHASE_NEGATIVE
-  if [ $(echo "${f_BUY_PRICE_LAST_RATE_DIFF} < ${SELL_PERCENTAGE_FROM_LAST_PURCHASE_NEGATIVE}" | bc -l) -ne 0 ]
+  if [ -z ${SELL_PERCENTAGE_FROM_LAST_PURCHASE_NEGATIVE} ]
   then
-    f_SELL="SELL_PERCENTAGE_FROM_LAST_PURCHASE_NEGATIVE(${SELL_PERCENTAGE_FROM_LAST_PURCHASE_NEGATIVE}%) > Last rate (${f_BUY_PRICE_LAST_RATE_DIFF}%)"
+    if [ $(echo "${f_BUY_PRICE_LAST_RATE_DIFF} < ${SELL_PERCENTAGE_FROM_LAST_PURCHASE_NEGATIVE}" | bc -l) -ne 0 ]
+    then
+      f_SELL="SELL_PERCENTAGE_FROM_LAST_PURCHASE_NEGATIVE(${SELL_PERCENTAGE_FROM_LAST_PURCHASE_NEGATIVE}%) > Last rate (${f_BUY_PRICE_LAST_RATE_DIFF}%)"
+    fi
   fi
 
 }