diff --git a/tests/css/test_grid_rows_columns_relative_units.py b/tests/css/test_grid_rows_columns_relative_units.py
new file mode 100644
index 000000000..e56bec65c
--- /dev/null
+++ b/tests/css/test_grid_rows_columns_relative_units.py
@@ -0,0 +1,42 @@
+"""
+Regression tests for #1406 https://github.com/Textualize/textual/issues/1406
+
+The scalars in grid-rows and grid-columns were not aware of the dimension
+they should be relative to.
+"""
+
+from textual.css.parse import parse_declarations
+from textual.css.scalar import Unit
+from textual.css.styles import Styles
+
+
+def test_grid_rows_columns_relative_units_are_correct():
+    """Ensure correct relative dimensions for programmatic assignments."""
+
+    styles = Styles()
+
+    styles.grid_columns = "1fr 5%"
+    fr, percent = styles.grid_columns
+    assert fr.percent_unit == Unit.WIDTH
+    assert percent.percent_unit == Unit.WIDTH
+
+    styles.grid_rows = "1fr 5%"
+    fr, percent = styles.grid_rows
+    assert fr.percent_unit == Unit.HEIGHT
+    assert percent.percent_unit == Unit.HEIGHT
+
+
+def test_styles_builder_uses_correct_relative_units_grid_rows_columns():
+    """Ensure correct relative dimensions for CSS parsed from files."""
+
+    CSS = "grid-rows: 1fr 5%; grid-columns: 1fr 5%;"
+
+    styles = parse_declarations(CSS, "test")
+
+    fr, percent = styles.grid_columns
+    assert fr.percent_unit == Unit.WIDTH
+    assert percent.percent_unit == Unit.WIDTH
+
+    fr, percent = styles.grid_rows
+    assert fr.percent_unit == Unit.HEIGHT
+    assert percent.percent_unit == Unit.HEIGHT