diff --git a/js/packages/binderhub-client/lib/index.js b/js/packages/binderhub-client/lib/index.js
index e138c0f0e..90ca683a4 100644
--- a/js/packages/binderhub-client/lib/index.js
+++ b/js/packages/binderhub-client/lib/index.js
@@ -118,30 +118,30 @@ export class BinderRepository {
     // Make a copy of the URL so we don't mangle the original
     let url = new URL(serverUrl);
     if (path) {
-      // strip trailing / from URL
-      url.pathname = url.pathname.replace(/\/$/, "");
-
+      // Ensure there is a trailing / in serverUrl
+      if (!url.pathname.endsWith("/")) {
+        url.pathname += "/";
+      }
       // trim leading '/' from path to launch users into
       path = path.replace(/(^\/)/g, "");
 
       if (pathType === "lab") {
         // The path is a specific *file* we should open with JupyterLab
-
         // trim trailing / on file paths
         path = path.replace(/(\/$)/g, "");
 
         // /doc/tree is safe because it allows redirect to files
-        url.pathname = url.pathname + "/doc/tree/" + encodeURI(path);
+        url = new URL("doc/tree/" + encodeURI(path), url);
       } else if (pathType === "file") {
         // The path is a specific file we should open with *classic notebook*
 
         // trim trailing / on file paths
         path = path.replace(/(\/$)/g, "");
-        // /tree is safe because it allows redirect to files
-        url.pathname = url.pathname + "/tree/" + encodeURI(path);
+
+        url = new URL("tree/" + encodeURI(path), url);
       } else {
         // pathType is 'url' and we should just pass it on
-        url.pathname = url.pathname + "/" + path;
+        url = new URL(path, url);
       }
     }
 
diff --git a/js/packages/binderhub-client/tests/index.test.js b/js/packages/binderhub-client/tests/index.test.js
index 1dd189459..37e11ac76 100644
--- a/js/packages/binderhub-client/tests/index.test.js
+++ b/js/packages/binderhub-client/tests/index.test.js
@@ -154,6 +154,26 @@ test("Get full redirect URL and deal with excessive slashes (with pathType=lab)"
   );
 });
 
+test("Get full redirect URL and deal with missing trailing slash", () => {
+  const br = new BinderRepository(
+    "gh/test/test",
+    new URL("https://test-binder.org/build"),
+  );
+  expect(
+    br
+      .getFullRedirectURL(
+        // Missing trailing slash here should not affect target url
+        "https://hub.test-binder.org/user/something",
+        "token",
+        "/directory/index.ipynb/",
+        "lab",
+      )
+      .toString(),
+  ).toBe(
+    "https://hub.test-binder.org/user/something/doc/tree/directory/index.ipynb?token=token",
+  );
+});
+
 test("Get full redirect URL and deal with excessive slashes (with pathType=file)", () => {
   const br = new BinderRepository(
     "gh/test/test",
@@ -233,3 +253,45 @@ describe(
   },
   10 * 1000,
 );
+
+test("Get full redirect URL and deal with query and encoded query (with pathType=url)", () => {
+  const br = new BinderRepository(
+    "gh/test/test",
+    new URL("https://test-binder.org/build"),
+  );
+  expect(
+    br
+      .getFullRedirectURL(
+        "https://hub.test-binder.org/user/something/",
+        "token",
+        // url path here is already url encoded
+        "endpoint?a=1%2F2&b=3%3F%2F",
+        "url",
+      )
+      .toString(),
+  ).toBe(
+    // url path here is exactly as encoded as passed in - not *double* encoded
+    "https://hub.test-binder.org/user/something/endpoint?a=1%2F2&b=3%3F%2F&token=token",
+  );
+});
+
+test("Get full redirect URL with nbgitpuller URL", () => {
+  const br = new BinderRepository(
+    "gh/test/test",
+    new URL("https://test-binder.org/build"),
+  );
+  expect(
+    br
+      .getFullRedirectURL(
+        "https://hub.test-binder.org/user/something/",
+        "token",
+        // urlpath is not actually url encoded - note that / is / not %2F
+        "git-pull?repo=https://github.com/alperyilmaz/jupyterlab-python-intro&urlpath=lab/tree/jupyterlab-python-intro/&branch=master",
+        "url",
+      )
+      .toString(),
+  ).toBe(
+    // generated URL path here *is* url encoded
+    "https://hub.test-binder.org/user/something/git-pull?repo=https%3A%2F%2Fgithub.com%2Falperyilmaz%2Fjupyterlab-python-intro&urlpath=lab%2Ftree%2Fjupyterlab-python-intro%2F&branch=master&token=token",
+  );
+});