diff --git a/stb_ds.h b/stb_ds.h
index e84c82d1d..a20968529 100644
--- a/stb_ds.h
+++ b/stb_ds.h
@@ -536,7 +536,7 @@ extern void * stbds_shmode_func(size_t elemsize, int mode);
 #define stbds_temp_key(t) (*(char **) stbds_header(t)->hash_table)
 
 #define stbds_arrsetcap(a,n)   (stbds_arrgrow(a,0,n))
-#define stbds_arrsetlen(a,n)   ((stbds_arrcap(a) < (size_t) (n) ? stbds_arrsetcap((a),(size_t)(n)),0 : 0), (a) ? stbds_header(a)->length = (size_t) (n) : 0)
+#define stbds_arrsetlen(a,n)   (((ptrdiff_t) stbds_arrcap(a) < (ptrdiff_t) (n) ? stbds_arrsetcap((a),(size_t)(n)),0 : 0), (a) ? stbds_header(a)->length = (size_t) (n) : 0)
 #define stbds_arrcap(a)        ((a) ? stbds_header(a)->capacity : 0)
 #define stbds_arrlen(a)        ((a) ? (ptrdiff_t) stbds_header(a)->length : 0)
 #define stbds_arrlenu(a)       ((a) ?             stbds_header(a)->length : 0)