diff --git a/icalendar_test.ts b/icalendar_test.ts
index 3927868..5707e11 100644
--- a/icalendar_test.ts
+++ b/icalendar_test.ts
@@ -225,3 +225,34 @@ Deno.test("expandRecurrences - object rrule with until", () => {
   assertEquals(results[0].recurrent, true);
 });
 
+
+Deno.test("expandRecurrences - object rrule with byday (Reproduction)", () => {
+  const now = new Date();
+  const start = new Date(now.getTime() - 10 * 86400000); 
+  const startStr = localDateString(start);
+
+  const icsEvent = {
+    summary: "Object RRULE BYDAY Event",
+    start: startStr,
+    rrule: { frequency: "WEEKLY", byday: [{ day: "MO" }, { day: "WE" }] } 
+  };
+  
+  // Spy on console.error
+  let errorLogged = false;
+  const originalConsoleError = console.error;
+  console.error = (...args) => {
+    if (args[0].includes("Error expanding recurrence for Object RRULE BYDAY Event") && 
+        args[1].message.includes("Invalid weekday string: [object Object]")) {
+      errorLogged = true;
+    }
+  };
+
+  try {
+    expandRecurrences(icsEvent, 30);
+  } finally {
+    console.error = originalConsoleError;
+  }
+
+  assert(errorLogged, "Should have logged an error for invalid BYDAY object values");
+});
+