Combine lemon juice, water and mint extract in a medium sauce pot.
Stir in pectin; bring to a rolling boil over high heat.
Add sugar and return to a rolling boil.
Boil hard 1 minute, stirring constantly.
Remove from heat.
Skim foam if necessary.
Pour hot into hot, sterilized jars, leaving 1/4 inch head space.
Process 5 minutes in boiling water bath.