diff --git a/tests/unit/test_isort.py b/tests/unit/test_isort.py
index c241e325..71681a2f 100644
--- a/tests/unit/test_isort.py
+++ b/tests/unit/test_isort.py
@@ -5562,6 +5562,21 @@ def seekable(self):
     assert identified_imports == [":1 import m2", ":2 import m1"]
 
 
+def test_unindented_comments_issue_1899():
+    """Ensure unindented comments in indented blocks are handled correctly"""
+
+    test_input = """
+import sys
+
+if True:
+# this comment will get cut off
+    import os
+
+    """
+
+    assert isort.code(test_input) == test_input
+
+
 def test_split_on_trailing_comma() -> None:
     test_input = "from lib import (a, b, c,)"
     expected_output = """from lib import (