diff --git a/pkg/eval/vals/index_list.go b/pkg/eval/vals/index_list.go
index 1bd9ef51..c573f64c 100644
--- a/pkg/eval/vals/index_list.go
+++ b/pkg/eval/vals/index_list.go
@@ -129,7 +129,11 @@ func parseIndexString(s string, n int) (slice bool, i int, j int, err error) {
 		}
 		if sep == "..=" {
 			// TODO: Handle j == MaxInt-1
-			j++
+			if j == -1 { // subtle corner case that is same as no high value
+				j = n
+			} else {
+				j++
+			}
 		}
 	}
 	// Two numbers
diff --git a/pkg/eval/vals/index_test.go b/pkg/eval/vals/index_test.go
index 25bbce4a..81c6f582 100644
--- a/pkg/eval/vals/index_test.go
+++ b/pkg/eval/vals/index_test.go
@@ -34,6 +34,7 @@ func TestIndex(t *testing.T) {
 		Args("abc", "1..=").Rets("bc", nil),
 		Args("abc", "..=1").Rets("ab", nil),
 		Args("abc", "..=").Rets("abc", nil),
+		Args("abc", "..=-1").Rets("abc", nil),
 		// String slices not at rune boundary.
 		Args("你好", "2..").Rets(Any, errIndexNotAtRuneBoundary),
 		Args("你好", "..2").Rets(Any, errIndexNotAtRuneBoundary),
@@ -92,6 +93,7 @@ func TestIndex(t *testing.T) {
 		Args(li4, "..=-2").Rets(eq(MakeList("foo", "bar", "lorem")), nil),
 		Args(li4, "3..=").Rets(eq(MakeList("ipsum")), nil),
 		Args(li4, "..=").Rets(eq(li4), nil),
+		Args(li4, "..=-1").Rets(eq(li4), nil),
 
 		// Slice index out of range.
 		Args(li4, "-5..1").Rets(nil, errs.OutOfRange{