diff --git a/user/usertests.c b/user/usertests.c
index af3e5db..fe3ae49 100644
--- a/user/usertests.c
+++ b/user/usertests.c
@@ -1757,7 +1757,7 @@ sbrkarg(char *s)
     printf("%s: open sbrk failed\n", s);
     exit(1);
   }
-  if ((n = write(fd, a, 10)) < 0) {
+  if ((n = write(fd, a, PGSIZE)) < 0) {
     printf("%s: write sbrk failed\n", s);
     exit(1);
   }