diff --git a/unit_tests/expr.suite/string-funcs.lsl b/unit_tests/expr.suite/string-funcs.lsl
index 11f701d..a2108fd 100644
--- a/unit_tests/expr.suite/string-funcs.lsl
+++ b/unit_tests/expr.suite/string-funcs.lsl
@@ -216,6 +216,7 @@
 , llReplaceSubString("cabadabaeaba", "", "faba", 0)
 , llReplaceSubString("cabadabaeaba", "", "faba", 1)
 , llReplaceSubString("cabadabaeaba", "", "faba", 20)
+, llReplaceSubString("aaaaaaaab", "aab", "ab", -3)
 , llReplaceSubString("", "", "faba", -2)
 , llReplaceSubString("", "", "faba", -1)
 , llReplaceSubString("", "", "faba", 0)
diff --git a/unit_tests/expr.suite/string-funcs.out b/unit_tests/expr.suite/string-funcs.out
index 128c8fc..82fbdf7 100644
--- a/unit_tests/expr.suite/string-funcs.out
+++ b/unit_tests/expr.suite/string-funcs.out
@@ -216,6 +216,7 @@
 , "cabadabaeaba"
 , "cabadabaeaba"
 , "cabadabaeaba"
+, "aaaaaaab"
 , ""
 , ""
 , ""