diff --git a/src/testdir/test_channel.vim b/src/testdir/test_channel.vim
index 8e29d32..363b5cd 100644
--- a/src/testdir/test_channel.vim
+++ b/src/testdir/test_channel.vim
@@ -183,7 +183,7 @@
   call assert_equal('got it', s:responseMsg)
 
   " Collect garbage, tests that our handle isn't collected.
-  call garbagecollect_for_testing()
+  call test_garbagecollect_now()
 
   " check setting options (without testing the effect)
   call ch_setoptions(handle, {'callback': 's:NotUsed'})
@@ -1302,7 +1302,7 @@
 func Test_using_freed_memory()
   let g:a = job_start(['ls'])
   sleep 10m
-  call garbagecollect_for_testing()
+  call test_garbagecollect_now()
 endfunc
 
 
diff --git a/src/testdir/test_expr.vim b/src/testdir/test_expr.vim
index 2cd9625..142455b 100644
--- a/src/testdir/test_expr.vim
+++ b/src/testdir/test_expr.vim
@@ -85,7 +85,7 @@
 endfunc
 
 func Test_loop_over_null_list()
-  let null_list = submatch(1, 1)
+  let null_list = test_null_list()
   for i in null_list
     call assert_true(0, 'should not get here')
   endfor