diff --git a/src/channel.c b/src/channel.c
index 83d057d..72484ec 100644
--- a/src/channel.c
+++ b/src/channel.c
@@ -458,8 +458,7 @@
 	ch_next = ch->ch_next;
 	if ((ch->ch_copyID & mask) != (copyID & mask))
 	{
-	    /* Free the channel and ordinary items it contains, but don't
-	     * recurse into Lists, Dictionaries etc. */
+	    /* Free the channel struct itself. */
 	    channel_free_channel(ch);
 	}
     }
@@ -4006,6 +4005,17 @@
     }
 }
 
+/*
+ * Return TRUE if the job should not be freed yet.  Do not free the job when
+ * it has not ended yet and there is a "stoponexit" flag or an exit callback.
+ */
+    static int
+job_still_useful(job_T *job)
+{
+    return job->jv_status == JOB_STARTED
+		   && (job->jv_stoponexit != NULL || job->jv_exit_cb != NULL);
+}
+
     void
 job_unref(job_T *job)
 {
@@ -4013,8 +4023,7 @@
     {
 	/* Do not free the job when it has not ended yet and there is a
 	 * "stoponexit" flag or an exit callback. */
-	if (job->jv_status != JOB_STARTED
-		|| (job->jv_stoponexit == NULL && job->jv_exit_cb == NULL))
+	if (!job_still_useful(job))
 	{
 	    job_free(job);
 	}
@@ -4036,7 +4045,8 @@
     job_T	*job;
 
     for (job = first_job; job != NULL; job = job->jv_next)
-	if ((job->jv_copyID & mask) != (copyID & mask))
+	if ((job->jv_copyID & mask) != (copyID & mask)
+						    && !job_still_useful(job))
 	{
 	    /* Free the channel and ordinary items it contains, but don't
 	     * recurse into Lists, Dictionaries etc. */
@@ -4055,10 +4065,10 @@
     for (job = first_job; job != NULL; job = job_next)
     {
 	job_next = job->jv_next;
-	if ((job->jv_copyID & mask) != (copyID & mask))
+	if ((job->jv_copyID & mask) != (copyID & mask)
+						    && !job_still_useful(job))
 	{
-	    /* Free the channel and ordinary items it contains, but don't
-	     * recurse into Lists, Dictionaries etc. */
+	    /* Free the job struct itself. */
 	    job_free_job(job);
 	}
     }
diff --git a/src/eval.c b/src/eval.c
index a14a721..8658045 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -373,6 +373,7 @@
     {VV_NAME("null",		 VAR_SPECIAL), VV_RO},
     {VV_NAME("none",		 VAR_SPECIAL), VV_RO},
     {VV_NAME("vim_did_enter",	 VAR_NUMBER), VV_RO},
+    {VV_NAME("testing",		 VAR_NUMBER), 0},
 };
 
 /* shorthand */
@@ -580,6 +581,7 @@
 static void f_foreground(typval_T *argvars, typval_T *rettv);
 static void f_function(typval_T *argvars, typval_T *rettv);
 static void f_garbagecollect(typval_T *argvars, typval_T *rettv);
+static void f_garbagecollect_for_testing(typval_T *argvars, typval_T *rettv);
 static void f_get(typval_T *argvars, typval_T *rettv);
 static void f_getbufline(typval_T *argvars, typval_T *rettv);
 static void f_getbufvar(typval_T *argvars, typval_T *rettv);
@@ -1029,7 +1031,7 @@
     ga_clear(&ga_scripts);
 
     /* unreferenced lists and dicts */
-    (void)garbage_collect();
+    (void)garbage_collect(FALSE);
 
     /* functions */
     free_all_functions();
@@ -6889,6 +6891,9 @@
     return current_copyID;
 }
 
+/* Used by get_func_tv() */
+static garray_T funcargs = GA_EMPTY;
+
 /*
  * Garbage collection for lists and dictionaries.
  *
@@ -6911,10 +6916,11 @@
 
 /*
  * Do garbage collection for lists and dicts.
+ * When "testing" is TRUE this is called from garbagecollect_for_testing().
  * Return TRUE if some memory was freed.
  */
     int
-garbage_collect(void)
+garbage_collect(int testing)
 {
     int		copyID;
     int		abort = FALSE;
@@ -6928,10 +6934,13 @@
     tabpage_T	*tp;
 #endif
 
-    /* Only do this once. */
-    want_garbage_collect = FALSE;
-    may_garbage_collect = FALSE;
-    garbage_collect_at_exit = FALSE;
+    if (!testing)
+    {
+	/* Only do this once. */
+	want_garbage_collect = FALSE;
+	may_garbage_collect = FALSE;
+	garbage_collect_at_exit = FALSE;
+    }
 
     /* We advance by two because we add one for items referenced through
      * previous_funccal. */
@@ -6989,6 +6998,11 @@
 	abort = abort || set_ref_in_ht(&fc->l_avars.dv_hashtab, copyID, NULL);
     }
 
+    /* function call arguments, if v:testing is set. */
+    for (i = 0; i < funcargs.ga_len; ++i)
+	abort = abort || set_ref_in_item(((typval_T **)funcargs.ga_data)[i],
+							  copyID, NULL, NULL);
+
     /* v: vars */
     abort = abort || set_ref_in_ht(&vimvarht, copyID, NULL);
 
@@ -7034,7 +7048,7 @@
 	if (did_free_funccal)
 	    /* When a funccal was freed some more items might be garbage
 	     * collected, so run again. */
-	    (void)garbage_collect();
+	    (void)garbage_collect(testing);
     }
     else if (p_verbose > 0)
     {
@@ -8424,6 +8438,7 @@
     {"foreground",	0, 0, f_foreground},
     {"function",	1, 3, f_function},
     {"garbagecollect",	0, 1, f_garbagecollect},
+    {"garbagecollect_for_testing",	0, 0, f_garbagecollect_for_testing},
     {"get",		2, 3, f_get},
     {"getbufline",	2, 3, f_getbufline},
     {"getbufvar",	2, 3, f_getbufvar},
@@ -8896,8 +8911,26 @@
 	ret = FAIL;
 
     if (ret == OK)
+    {
+	int		i = 0;
+
+	if (get_vim_var_nr(VV_TESTING))
+	{
+	    /* Prepare for calling garbagecollect_for_testing(), need to know
+	     * what variables are used on the call stack. */
+	    if (funcargs.ga_itemsize == 0)
+		ga_init2(&funcargs, (int)sizeof(typval_T *), 50);
+	    for (i = 0; i < argcount; ++i)
+		if (ga_grow(&funcargs, 1) == OK)
+		    ((typval_T **)funcargs.ga_data)[funcargs.ga_len++] =
+								  &argvars[i];
+	}
+
 	ret = call_func(name, len, rettv, argcount, argvars,
 		 firstline, lastline, doesrange, evaluate, partial, selfdict);
+
+	funcargs.ga_len -= i;
+    }
     else if (!aborting())
     {
 	if (argcount == MAX_FUNC_ARGS)
@@ -12318,6 +12351,17 @@
 }
 
 /*
+ * "garbagecollect_for_testing()" function
+ */
+    static void
+f_garbagecollect_for_testing(typval_T *argvars UNUSED, typval_T *rettv UNUSED)
+{
+    /* This is dangerous, any Lists and Dicts used internally may be freed
+     * while still in use. */
+    garbage_collect(TRUE);
+}
+
+/*
  * "get()" function
  */
     static void
diff --git a/src/getchar.c b/src/getchar.c
index 4a225e1..c771117 100644
--- a/src/getchar.c
+++ b/src/getchar.c
@@ -1523,7 +1523,7 @@
     updatescript(0);
 #ifdef FEAT_EVAL
     if (may_garbage_collect)
-	garbage_collect();
+	garbage_collect(FALSE);
 #endif
 }
 
@@ -1571,7 +1571,7 @@
     /* Do garbage collection when garbagecollect() was called previously and
      * we are now at the toplevel. */
     if (may_garbage_collect && want_garbage_collect)
-	garbage_collect();
+	garbage_collect(FALSE);
 #endif
 
     /*
diff --git a/src/main.c b/src/main.c
index dc7b702..ee37500 100644
--- a/src/main.c
+++ b/src/main.c
@@ -1531,7 +1531,7 @@
 #endif
 #ifdef FEAT_EVAL
     if (garbage_collect_at_exit)
-	garbage_collect();
+	garbage_collect(FALSE);
 #endif
 #if defined(WIN32) && defined(FEAT_MBYTE)
     free_cmd_argsW();
diff --git a/src/proto/eval.pro b/src/proto/eval.pro
index 38392b9..9fda13c 100644
--- a/src/proto/eval.pro
+++ b/src/proto/eval.pro
@@ -49,7 +49,6 @@
 list_T *list_alloc(void);
 int rettv_list_alloc(typval_T *rettv);
 void list_unref(list_T *l);
-void list_free_internal(list_T *l);
 void list_free(list_T *l);
 listitem_T *listitem_alloc(void);
 void listitem_free(listitem_T *item);
@@ -66,14 +65,13 @@
 void list_insert(list_T *l, listitem_T *ni, listitem_T *item);
 void vimlist_remove(list_T *l, listitem_T *item, listitem_T *item2);
 int get_copyID(void);
-int garbage_collect(void);
+int garbage_collect(int testing);
 int set_ref_in_ht(hashtab_T *ht, int copyID, list_stack_T **list_stack);
 int set_ref_in_list(list_T *l, int copyID, ht_stack_T **ht_stack);
 int set_ref_in_item(typval_T *tv, int copyID, ht_stack_T **ht_stack, list_stack_T **list_stack);
 dict_T *dict_alloc(void);
 int rettv_dict_alloc(typval_T *rettv);
 void dict_unref(dict_T *d);
-void dict_free_internal(dict_T *d);
 void dict_free(dict_T *d);
 dictitem_T *dictitem_alloc(char_u *key);
 void dictitem_free(dictitem_T *item);
diff --git a/src/testdir/runtest.vim b/src/testdir/runtest.vim
index 4d75af3..2b38981 100644
--- a/src/testdir/runtest.vim
+++ b/src/testdir/runtest.vim
@@ -60,6 +60,9 @@
 
 let s:srcdir = expand('%:p:h:h')
 
+" Prepare for calling garbagecollect_for_testing().
+let v:testing = 1
+
 " Support function: get the alloc ID by name.
 function GetAllocId(name)
   exe 'split ' . s:srcdir . '/alloc.h'
diff --git a/src/testdir/test_channel.vim b/src/testdir/test_channel.vim
index e134527..05df50a 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()
+  call garbagecollect_for_testing()
 
   " check setting options (without testing the effect)
   call ch_setoptions(handle, {'callback': 's:NotUsed'})
@@ -1231,7 +1231,7 @@
   call assert_fails('call job_start("")', 'E474:')
 endfunc
 
-" This leaking memory.
+" This was leaking memory.
 func Test_partial_in_channel_cycle()
   let d = {}
   let d.a = function('string', [d])
@@ -1243,5 +1243,13 @@
   unlet d
 endfunc
 
+func Test_using_freed_memory()
+  let g:a = job_start(['ls'])
+  sleep 10m
+  call garbagecollect_for_testing()
+endfunc
+
+
+
 " Uncomment this to see what happens, output is in src/testdir/channellog.
 " call ch_logfile('channellog', 'w')
diff --git a/src/version.c b/src/version.c
index cf7d48c..6c94bc6 100644
--- a/src/version.c
+++ b/src/version.c
@@ -749,6 +749,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1727,
+/**/
     1726,
 /**/
     1725,
diff --git a/src/vim.h b/src/vim.h
index 36cc19a..9e2ab21 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -1868,7 +1868,8 @@
 #define VV_NULL		65
 #define VV_NONE		66
 #define VV_VIM_DID_ENTER 67
-#define VV_LEN		68	/* number of v: vars */
+#define VV_TESTING	68
+#define VV_LEN		69	/* number of v: vars */
 
 /* used for v_number in VAR_SPECIAL */
 #define VVAL_FALSE	0L