use url.searchParams

src/client/js/components/RevisionComparer/RevisionComparer.jsx

@@ -45,8 +45,10 @@ const RevisionComparer = (props) => {
     const { path } = revisionComparerContainer.pageContainer.state;
     const { sourceRevision, targetRevision } = revisionComparerContainer.state;
 
-    const urlParams = (sourceRevision && targetRevision ? `${path}?compare=${sourceRevision._id}...${targetRevision._id}` : '');
-    const url = new URL(urlParams, origin);
+    const urlParams = (sourceRevision && targetRevision ? `${sourceRevision._id}...${targetRevision._id}` : '');
+
+    const url = new URL(path, origin);
+    url.searchParams.set('compare', urlParams);
 
     return encodeSpaces(decodeURI(url));
   };