diff --git a/collects/racket/draw/unsafe/jpeg.rkt b/collects/racket/draw/unsafe/jpeg.rkt
index 6f4ad4e5d5..47895374f3 100644
--- a/collects/racket/draw/unsafe/jpeg.rkt
+++ b/collects/racket/draw/unsafe/jpeg.rkt
@@ -19,7 +19,7 @@
 (define-ffi-definer define-jpeg/private jpeg-lib)
 
 (define _j_common_ptr _pointer)
-(define _size_t _long)
+(define _size_t _intptr)
 (define _JDIMENSION _uint)
 (define _J_COLOR_SPACE _int)
 (define _J_DCT_METHOD _int)