The following statement is from the contract Peter signed with his Homeowners' Association (HOA). "Overnight parking on community streets is prohibited. For the purpose of this contract, 'overnight' will be defined as the hours between 11:00 p. m. and 4:00 a. m. The HOA will monitor overnight parking not less than once every calendar week with nightly patrols by community security.

"In the event a car is found parked on community streets overnight and that ownership of the offending car can accurately be verified as a community homeowner, the homeowner will receive one (1) written warning asking him or her to correct the situation. A second and third infraction by the same homeowner, whether or not it is with the same car, will result in a monetary fine as permitted by CC&R guidelines and HOA bylaws. Further infractions (past 3) will result in monetary fines in addition to the towing of the car at the homeowner's expense."

After parking his car at 12:30 a. m. last night, Peter was approached by the on-duty neighborhood security guard. The guard told Peter that it was against established HOA rules to park overnight on community streets and reminded Peter that he had signed the contract agreeing to adhere to those rules. He then asked Peter to move the car onto his driveway and warned him that a second offense would result in a monetary fine.

Which of the following facts invalidates the contract between Peter and the HOA?