diff --git a/files/validate_postgresql_connection.sh b/files/validate_postgresql_connection.sh
index 2b3d629..1c3506c 100644
--- a/files/validate_postgresql_connection.sh
+++ b/files/validate_postgresql_connection.sh
@@ -1,34 +1,34 @@
 #!/bin/sh
 
 # usage is: validate_db_connection 2 50 psql
 
 SLEEP=$1
 TRIES=$2
 PSQL=$3
 
 STATE=1
 
 c=1
 
 while [ $c -le $TRIES ]
 do
   echo $c
   if [ $c -gt 1 ]
   then
     echo 'sleeping'
     sleep $SLEEP
   fi
 
   /bin/echo "SELECT 1" | $PSQL
   STATE=$?
 
   if [ $STATE -eq 0 ]
   then
     exit 0
   fi
-$c++
+  c=$((c+1))
 done
 
 echo 'Unable to connect to postgresql'
 
 exit 1