diff --git a/atpbar/stream/output.py b/atpbar/stream/output.py
index 61ef5bd..fca90a6 100644
--- a/atpbar/stream/output.py
+++ b/atpbar/stream/output.py
@@ -18,17 +18,11 @@ def __init__(self, queue: StreamQueue, fd: FD) -> None:
         self.buffer = ''
 
     def write(self, s: str) -> int:
-        # sys.__stdout__.write(repr(s))
-        # sys.__stdout__.write('\n')
+        if not isinstance(s, str):
+            # The same error message as `sys.stdout.write()`
+            raise TypeError(f'write() argument must be str, not {type(s).__name__}')
 
-        try:
-            endswith_n = s.endswith('\n')
-        except:
-            self.flush()
-            self.queue.put((s, self.fd))
-            return len(s)
-
-        if endswith_n:
+        if s.endswith('\n'):
             self.buffer += s
             self.flush()
             return len(s)
diff --git a/tests/stream/output/test_stateful.py b/tests/stream/output/test_output_stream.py
similarity index 89%
rename from tests/stream/output/test_stateful.py
rename to tests/stream/output/test_output_stream.py
index 5e419e0..fbd7e18 100644
--- a/tests/stream/output/test_stateful.py
+++ b/tests/stream/output/test_output_stream.py
@@ -1,5 +1,6 @@
 from unittest.mock import sentinel
 
+import pytest
 from hypothesis import given, settings
 from hypothesis import strategies as st
 
@@ -7,6 +8,12 @@
 from tests.stream.st import st_text
 
 
+def test_type_error() -> None:
+    stream = OutputStream(Queue(), sentinel.fd)
+    with pytest.raises(TypeError):
+        stream.write(123)  # type: ignore
+
+
 class StatefulTest:
     def __init__(self, data: st.DataObject) -> None:
         self.draw = data.draw