diff --git a/dom/url/URLSearchParams.cpp b/dom/url/URLSearchParams.cpp
index ad23460f3..f762299f8 100644
--- a/dom/url/URLSearchParams.cpp
+++ b/dom/url/URLSearchParams.cpp
@@ -358,7 +358,7 @@ URLSearchParams::Constructor(const GlobalObject& aGlobal,
       sp->Append(entry.mKey, entry.mValue);
     }
   } else {
-    MOZ_CRASH("This should not happen.");
+    MOZ_CRASH("URLSearchParams: Invalid string");
   }
 
   return sp.forget();