The current make-null-gl-array fails to run as currently defined. When called with (gl:make-null-gl-array :unsigned-short), SBCL gives the following error: 0 fell through CTYPECASE expression. Wanted one of (SYMBOL FUNCTION). [Condition of type SB-KERNEL:CASE-FAILURE] The problem seems simply to be that the arguments when calling MAKE-GL-ARRAY-FROM-POINTER are reversed. Specifically, instead of (make-gl-array-from-pointer (null-pointer) 0 type) the body of MAKE-NULL-GL-ARRAY should be (make-gl-array-from-pointer (null-pointer) type 0) Mason