diff --git a/Userland/Libraries/LibWeb/DOM/Document.cpp b/Userland/Libraries/LibWeb/DOM/Document.cpp
index a0ef87151f..0369b42a3c 100644
--- a/Userland/Libraries/LibWeb/DOM/Document.cpp
+++ b/Userland/Libraries/LibWeb/DOM/Document.cpp
@@ -1006,7 +1006,7 @@ String Document::cookie(Cookie::Source source)
     return {};
 }
 
-void Document::set_cookie(String cookie_string, Cookie::Source source)
+void Document::set_cookie(String const& cookie_string, Cookie::Source source)
 {
     auto cookie = Cookie::parse_cookie(cookie_string);
     if (!cookie.has_value())
diff --git a/Userland/Libraries/LibWeb/DOM/Document.h b/Userland/Libraries/LibWeb/DOM/Document.h
index 1b67116601..529a236e8f 100644
--- a/Userland/Libraries/LibWeb/DOM/Document.h
+++ b/Userland/Libraries/LibWeb/DOM/Document.h
@@ -56,7 +56,7 @@ public:
     virtual ~Document() override;
 
     String cookie(Cookie::Source = Cookie::Source::NonHttp);
-    void set_cookie(String, Cookie::Source = Cookie::Source::NonHttp);
+    void set_cookie(String const&, Cookie::Source = Cookie::Source::NonHttp);
 
     String referrer() const;