diff --git a/system/readline/readline_common.c b/system/readline/readline_common.c
index 4fe7c6c0b..13750fe8e 100644
--- a/system/readline/readline_common.c
+++ b/system/readline/readline_common.c
@@ -302,7 +302,7 @@ static void tab_completion(FAR struct rl_common_s *vtbl, char *buf,
                    * matches.
                    */
 
-                  if (name[j] != tmp_name[j])
+                  if (j < sizeof(tmp_name) && name[j] != tmp_name[j])
                     {
                       tmp_name[j] = '\0';
                     }
@@ -337,7 +337,7 @@ static void tab_completion(FAR struct rl_common_s *vtbl, char *buf,
                    * matches.
                    */
 
-                  if (name[j] != tmp_name[j])
+                  if (j < sizeof(tmp_name) && name[j] != tmp_name[j])
                     {
                       tmp_name[j] = '\0';
                     }