diff --git a/src/main/kotlin/html4tree/main.kt b/src/main/kotlin/html4tree/main.kt
index 0972fa2c..f54e1035 100644
--- a/src/main/kotlin/html4tree/main.kt
+++ b/src/main/kotlin/html4tree/main.kt
@@ -236,15 +236,8 @@ fun String.escapeHtml(): String {
     var sb: StringBuilder? = null
     for (i in 0 until this.length) {
         val c = this[i]
-        val replacement = when (c) {
-            '&' -> "&"
-            '<' -> "&lt;"
-            '>' -> "&gt;"
-            '"' -> "&quot;"
-            '\'' -> "&#x27;"
-            '`' -> "&#x60;"
-            else -> null
-        }
+        val cInt = c.toInt()
+        val replacement = if (cInt < 128) Constants.HTML_ESCAPE_TABLE[cInt] else null
         if (replacement != null) {
             if (sb == null) {
                 sb = StringBuilder(this.length + 16)
@@ -496,6 +489,16 @@ fun help() {
 }
 
 private object Constants {
+    @JvmField
+    val HTML_ESCAPE_TABLE: Array<String?> = Array<String?>(128) { null }.apply {
+        this['&'.toInt()] = "&amp;"
+        this['<'.toInt()] = "&lt;"
+        this['>'.toInt()] = "&gt;"
+        this['"'.toInt()] = "&quot;"
+        this['\''.toInt()] = "&#x27;"
+        this['`'.toInt()] = "&#x60;"
+    }
+
     @JvmField
     val defaultSensitiveFiles = listOf(".git", ".env", ".ssh", ".htpasswd", ".htaccess", "id_rsa", "id_ed25519", "secrets.yml", ".html4ignore", ".DS_Store", ".aws", ".kube", ".npmrc", ".gnupg", "config.json", "credentials.json")
 
diff --git a/src/test/kotlin/html4tree/EscapeHtmlLookupContractTest.kt b/src/test/kotlin/html4tree/EscapeHtmlLookupContractTest.kt
new file mode 100644
index 00000000..8df23e9d
--- /dev/null
+++ b/src/test/kotlin/html4tree/EscapeHtmlLookupContractTest.kt
@@ -0,0 +1,15 @@
+package html4tree
+
+import org.junit.Test
+import kotlin.test.assertEquals
+
+class EscapeHtmlLookupContractTest {
+    @Test
+    fun escapeHtmlPreservesProtectedMappingAcrossAsciiAndUnicode() {
+        assertEquals("", "".escapeHtml())
+        assertEquals("plain ASCII 123", "plain ASCII 123".escapeHtml())
+        assertEquals("&amp;&lt;&gt;&quot;&#x27;&#x60;", "&<>\"'`".escapeHtml())
+        assertEquals("한글 中文 日本語 العربية עברית", "한글 中文 日本語 العربية עברית".escapeHtml())
+        assertEquals("A&amp;한글&lt;עברית&gt;Z", "A&한글<עברית>Z".escapeHtml())
+    }
+}