diff --git a/rich/progress.py b/rich/progress.py
index bbbdf70ef..e904b8b24 100644
--- a/rich/progress.py
+++ b/rich/progress.py
@@ -427,7 +427,9 @@ def render(self, task: "Task") -> Text:
             )
         else:
             unit, suffix = filesize.pick_unit_and_suffix(
-                total, ["bytes", "KB", "MB", "GB", "TB", "PB", "EB", "ZB", "YB"], 1000
+                total,
+                ["bytes", "kB", "MB", "GB", "TB", "PB", "EB", "ZB", "YB"],
+                1000,
             )
         completed_ratio = completed / unit
         total_ratio = total / unit
diff --git a/tests/test_progress.py b/tests/test_progress.py
index 2dd53ccd2..1941448d9 100644
--- a/tests/test_progress.py
+++ b/tests/test_progress.py
@@ -123,7 +123,7 @@ def test_download_progress_uses_decimal_units() -> None:
     column = DownloadColumn()
     test_task = Task(1, "test", 1000, 500, _get_time=lambda: 1.0)
     rendered_progress = str(column.render(test_task))
-    expected = "0.5/1.0 KB"
+    expected = "0.5/1.0 kB"
     assert rendered_progress == expected