diff --git a/src/check_expr.cpp b/src/check_expr.cpp
index dc2e44533..943b1972d 100644
--- a/src/check_expr.cpp
+++ b/src/check_expr.cpp
@@ -2647,9 +2647,9 @@ bool check_index_value(CheckerContext *c, bool open_range, Ast *index_value, i64
 			if (value) *value = v;
 			bool out_of_bounds = false;
 			if (open_range) {
-				out_of_bounds = v > max_count;
+				out_of_bounds = v > max_count+1;
 			} else {
-				out_of_bounds = v >= max_count;
+				out_of_bounds = v > max_count;
 			}
 			if (v < 0) {
 				out_of_bounds = true;