diff --git a/src/testdir/test_vim9_assign.vim b/src/testdir/test_vim9_assign.vim
index c5f56c2..1d62ac1 100644
--- a/src/testdir/test_vim9_assign.vim
+++ b/src/testdir/test_vim9_assign.vim
@@ -847,6 +847,9 @@
   assert_equal(['sdf', 'asdf', 'end'], list3)
 
   v9.CheckDefExecFailure(['var ll = [1, 2, 3]', 'll[-4] = 6'], 'E684:')
+  v9.CheckDefExecFailure(['var ll = [1, 2, 3]', 'unlet ll[8 : 9]'], 'E684:')
+  v9.CheckDefExecFailure(['var ll = [1, 2, 3]', 'unlet ll[1 : -9]'], 'E684:')
+  v9.CheckDefExecFailure(['var ll = [1, 2, 3]', 'unlet ll[2 : 1]'], 'E684:')
 
   # type becomes list<any>
   var somelist = rand() > 0 ? [1, 2, 3] : ['a', 'b', 'c']
@@ -2193,6 +2196,10 @@
     'g:dd = {"a": 1, 2: 2}'
     'unlet g:dd[0z11]',
     ], 'E1029:', 2)
+  v9.CheckDefExecFailure([
+    'g:str = "a string"'
+    'unlet g:str[0]',
+    ], 'E1148: Cannot index a string', 2)
 
   # can compile unlet before variable exists
   g:someDict = {key: 'val'}
diff --git a/src/version.c b/src/version.c
index edac690..89a9fbb 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    4409,
+/**/
     4408,
 /**/
     4407,
diff --git a/src/vim9execute.c b/src/vim9execute.c
index 1c5dd74..317d1c3 100644
--- a/src/vim9execute.c
+++ b/src/vim9execute.c
@@ -1998,12 +1998,12 @@
     // Stack contains:
     // -2 index
     // -1 dict or list
+    SOURCING_LNUM = iptr->isn_lnum;
     if (tv_dest->v_type == VAR_DICT)
     {
 	// unlet a dict item, index must be a string
 	if (tv_idx->v_type != VAR_STRING && tv_idx->v_type != VAR_NUMBER)
 	{
-	    SOURCING_LNUM = iptr->isn_lnum;
 	    semsg(_(e_expected_str_but_got_str),
 			vartype_name(VAR_STRING),
 			vartype_name(tv_idx->v_type));
@@ -2020,7 +2020,6 @@
 		status = FAIL;
 	    else
 	    {
-		SOURCING_LNUM = iptr->isn_lnum;
 		if (tv_idx->v_type == VAR_STRING)
 		{
 		    key = tv_idx->vval.v_string;
@@ -2053,7 +2052,6 @@
     else if (tv_dest->v_type == VAR_LIST)
     {
 	// unlet a List item, index must be a number
-	SOURCING_LNUM = iptr->isn_lnum;
 	if (check_for_number(tv_idx) == FAIL)
 	{
 	    status = FAIL;
@@ -2072,7 +2070,6 @@
 
 		if (li == NULL)
 		{
-		    SOURCING_LNUM = iptr->isn_lnum;
 		    semsg(_(e_list_index_out_of_range_nr), n);
 		    status = FAIL;
 		}
@@ -2133,7 +2130,11 @@
 
 	    li = list_find_index(l, &n1);
 	    if (li == NULL)
+	    {
+		semsg(_(e_list_index_out_of_range_nr),
+						 (long)tv_idx1->vval.v_number);
 		status = FAIL;
+	    }
 	    else
 	    {
 		if (n1 < 0)
@@ -2143,7 +2144,10 @@
 		    listitem_T *li2 = list_find(l, n2);
 
 		    if (li2 == NULL)
+		    {
+			semsg(_(e_list_index_out_of_range_nr), n2);
 			status = FAIL;
+		    }
 		    else
 			n2 = list_idx_of_item(l, li2);
 		}