diff --git a/man/waybar-sway-workspaces.5.scd b/man/waybar-sway-workspaces.5.scd
index a65a999b..fc73a85a 100644
--- a/man/waybar-sway-workspaces.5.scd
+++ b/man/waybar-sway-workspaces.5.scd
@@ -87,6 +87,7 @@ warp-on-scroll: ++
 	Regex rules to map window class to an icon or preferred method of representation for a workspace's window.
 	Keys are the rules, while the values are the methods of representation.
 	Rules may specify `class<...>`, `title<...>`, or both in order to fine-tune the matching.
+	You may assign an empty value to a rule to have it ignored from generating any representation in workspaces.
 
 *window-rewrite-default*:
 	typeof: string ++
diff --git a/src/modules/sway/workspaces.cpp b/src/modules/sway/workspaces.cpp
index 0ca41d1c..8f273300 100644
--- a/src/modules/sway/workspaces.cpp
+++ b/src/modules/sway/workspaces.cpp
@@ -261,13 +261,17 @@ void Workspaces::updateWindows(const Json::Value &node, std::string &windows) {
       node["name"].isString()) {
     std::string title = g_markup_escape_text(node["name"].asString().c_str(), -1);
     std::string windowClass = node["app_id"].asString();
-    std::string windowReprKey = fmt::format("class<{}> title<{}>", windowClass, title);
-    std::string window = m_windowRewriteRules.get(windowReprKey);
-    // allow result to have formatting
-    window =
-        fmt::format(fmt::runtime(window), fmt::arg("name", title), fmt::arg("class", windowClass));
-    windows.append(window);
-    windows.append(m_formatWindowSeperator);
+
+    // Only add window rewrites that can be looked up
+    if (!windowClass.empty()) {
+      std::string windowReprKey = fmt::format("class<{}> title<{}>", windowClass, title);
+      std::string window = m_windowRewriteRules.get(windowReprKey);
+      // allow result to have formatting
+      window = fmt::format(fmt::runtime(window), fmt::arg("name", title),
+                           fmt::arg("class", windowClass));
+      windows.append(window);
+      windows.append(m_formatWindowSeperator);
+    }
   }
   for (const Json::Value &child : node["nodes"]) {
     updateWindows(child, windows);