ANSI Common Lisp   3 Evaluation and Compilation   3.5 Error Checking in Function Calls   3.5.1 Argument Mismatch Detection

3.5.1.6 Odd Number of Keyword Arguments

An odd number of arguments must not be supplied for the keyword parameters.

If this situation occurs in a safe call, an error of type program-error must be signaled unless keyword argument checking is suppressed as described in Section 3.4.1.4.1 Suppressing Keyword Argument Checking; and in an unsafe call the situation has undefined consequences.