diff --git a/tomlkit/_utils.py b/tomlkit/_utils.py
index a6ed9c6..f87fd7b 100644
--- a/tomlkit/_utils.py
+++ b/tomlkit/_utils.py
@@ -133,9 +133,11 @@ def flush(inc=1):
 
         return i + inc
 
+    found_sequences = {seq for seq in escape_sequences if seq in s}
+
     i = 0
     while i < len(s):
-        for seq in escape_sequences:
+        for seq in found_sequences:
             seq_len = len(seq)
             if s[i:].startswith(seq):
                 start = flush(seq_len)