Error in string comparison in if condition in bash shell

I need to read some properties from a config file and execute some commands if the properties match certain values. But when I try to compare the value with a string in if condition, it doesn't work.

Below is a small version of what I am trying to do.

#!/bin/bash
source config.file

echo "mode: $mode"

if [ "$mode" = "slow" ];
then 
echo "Mode is slow"
fi

The config file looks like this.

###config###
mode=slow
user=admin
password=pwd
###end###

The echo statement prints the values as "slow" but the if condition is never satisfied. What am I doing wrong?