diff --git a/AK/GenericLexer.cpp b/AK/GenericLexer.cpp
index 565ecf3917..4ea809973f 100644
--- a/AK/GenericLexer.cpp
+++ b/AK/GenericLexer.cpp
@@ -76,6 +76,13 @@ bool GenericLexer::next_is(const char* expected) const
     return true;
 }
 
+// Go back to the previous character
+void GenericLexer::retreat()
+{
+    ASSERT(m_index > 0);
+    m_index--;
+}
+
 // Consume a character and advance the parser index
 char GenericLexer::consume()
 {
diff --git a/AK/GenericLexer.h b/AK/GenericLexer.h
index ce5d123f16..854bc96a21 100644
--- a/AK/GenericLexer.h
+++ b/AK/GenericLexer.h
@@ -48,6 +48,8 @@ public:
     bool next_is(StringView) const;
     bool next_is(const char*) const;
 
+    void retreat();
+
     char consume();
     bool consume_specific(char);
     bool consume_specific(StringView);