diff --git a/jerry-core/ecma/builtin-objects/ecma-builtin-helpers.c b/jerry-core/ecma/builtin-objects/ecma-builtin-helpers.c
index 26d2a15b8..eea19bf1e 100644
--- a/jerry-core/ecma/builtin-objects/ecma-builtin-helpers.c
+++ b/jerry-core/ecma/builtin-objects/ecma-builtin-helpers.c
@@ -585,7 +585,9 @@ ecma_builtin_helper_string_prototype_object_index_of (ecma_string_t *original_st
 #if ENABLED (JERRY_ES2015)
     case ECMA_STRING_STARTS_WITH:
     {
-      if (pos_num + start > original_len)
+      const ecma_length_t search_len = ecma_string_get_length (search_str_p);
+
+      if (search_len + start > original_len)
       {
         break;
       }
@@ -687,7 +689,7 @@ ecma_builtin_helper_string_find_index (ecma_string_t *original_str_p, /**< index
     if (!search_len)
     {
       match_found = true;
-      *ret_index_p = first_index ? 0 : original_len;
+      *ret_index_p = first_index ? start_pos : original_len;
     }
     else
     {
diff --git a/tests/jerry/es2015/string-prototype-startswith.js b/tests/jerry/es2015/string-prototype-startswith.js
index 0effd36b4..3f23487f3 100644
--- a/tests/jerry/es2015/string-prototype-startswith.js
+++ b/tests/jerry/es2015/string-prototype-startswith.js
@@ -15,7 +15,10 @@
 var x = "My cat is awesome";
 assert (x.startsWith ("My"));
 assert (x.startsWith ("cat", 3));
+assert (x.startsWith ("awesome", 10));
 assert (x.startsWith (""));
+assert (x.startsWith ("", 1));
+assert (x.startsWith ("", 17));
 assert (x.startsWith ([]));
 
 assert (x.startsWith ("doggo") === false);