diff --git a/Userland/Libraries/LibWeb/URL/URLSearchParams.cpp b/Userland/Libraries/LibWeb/URL/URLSearchParams.cpp
index a9a0a74de9..fccdc8a801 100644
--- a/Userland/Libraries/LibWeb/URL/URLSearchParams.cpp
+++ b/Userland/Libraries/LibWeb/URL/URLSearchParams.cpp
@@ -234,7 +234,7 @@ void URLSearchParams::sort()
     update();
 }
 
-String URLSearchParams::to_string()
+String URLSearchParams::to_string() const
 {
     // return the serialization of this’s list.
     return url_encode(m_list, AK::URL::PercentEncodeSet::ApplicationXWWWFormUrlencoded);
diff --git a/Userland/Libraries/LibWeb/URL/URLSearchParams.h b/Userland/Libraries/LibWeb/URL/URLSearchParams.h
index a2cfe8c7e5..042c8e1109 100644
--- a/Userland/Libraries/LibWeb/URL/URLSearchParams.h
+++ b/Userland/Libraries/LibWeb/URL/URLSearchParams.h
@@ -41,7 +41,7 @@ public:
 
     void sort();
 
-    String to_string();
+    String to_string() const;
 
     using ForEachCallback = Function<JS::ThrowCompletionOr<void>(String const&, String const&)>;
     JS::ThrowCompletionOr<void> for_each(ForEachCallback);