diff --git a/solarfarmer/models/pvsystem/pvsystem.py b/solarfarmer/models/pvsystem/pvsystem.py
index c440480..2247e5c 100644
--- a/solarfarmer/models/pvsystem/pvsystem.py
+++ b/solarfarmer/models/pvsystem/pvsystem.py
@@ -1778,7 +1778,7 @@ def generate_mounting_specs(
         # the orientation is set to the plane in the layout
         if plant.flush_mount:
             height_from_ground = 0.1  # A small height of 10 cm
-            tilt_angle = 0.0
+            tilt_angle = plant.tilt
         else:
             height_from_ground = plant.mounting_height
             tilt_angle = plant.tilt if plant.tilt is not None else round(plant.latitude)
diff --git a/tests/test_construct_plant.py b/tests/test_construct_plant.py
index 40bae29..f8aaf65 100644
--- a/tests/test_construct_plant.py
+++ b/tests/test_construct_plant.py
@@ -7,6 +7,7 @@
 from solarfarmer.models.pvsystem.pvsystem import (
     construct_plant,
     design_plant,
+    generate_mounting_specs,
     generate_pan_file_supplements,
 )
 
@@ -122,6 +123,32 @@ def total_inverters(pv_plant):
         assert total_inverters(small_plant) < total_inverters(large_plant)
 
 
+class TestGenerateMountingSpecs:
+    """Regression tests for generate_mounting_specs()."""
+
+    def test_flush_mount_uses_plant_tilt(self):
+        """Flush-mount fixed systems should preserve plant.tilt in mounting specs."""
+        plant = PVSystem(
+            latitude=46.95,
+            longitude=7.44,
+            mounting="Fixed",
+            flush_mount=True,
+            tilt=15.0,
+        )
+
+        specs = generate_mounting_specs(
+            mounting_type_id="Mounting Type 1",
+            plant=plant,
+            are_modules_landscape=False,
+            rack_height=2.0,
+            y_spacing=0.02,
+        )
+
+        spec = specs["Mounting Type 1"]
+        assert spec.tilt == pytest.approx(15.0)
+        assert spec.height_of_lowest_edge_from_ground == pytest.approx(0.1)
+
+
 class TestSpecIdDerivation:
     """Verify spec IDs are derived via Path.stem (last-dot split), not split('.')[0]."""