diff --git a/masque/test/test_ports2data.py b/masque/test/test_ports2data.py
index 514ab9a..3f642ab 100644
--- a/masque/test/test_ports2data.py
+++ b/masque/test/test_ports2data.py
@@ -116,3 +116,17 @@ def test_data_to_ports_hierarchical_collision_is_atomic() -> None:
         data_to_ports([layer], lib, parent, max_depth=1)
 
     assert not parent.ports
+
+
+def test_data_to_ports_flat_bad_angle_warns_and_skips(
+        caplog: pytest.LogCaptureFixture,
+        ) -> None:
+    layer = (10, 0)
+    pat = Pattern()
+    pat.label(layer=layer, string="A:type1 nope", offset=(5, 0))
+
+    caplog.set_level("WARNING")
+    data_to_ports([layer], {}, pat)
+
+    assert not pat.ports
+    assert any('bad angle' in record.message for record in caplog.records)
diff --git a/masque/utils/ports2data.py b/masque/utils/ports2data.py
index 119ead1..44a0ec3 100644
--- a/masque/utils/ports2data.py
+++ b/masque/utils/ports2data.py
@@ -184,7 +184,14 @@ def data_to_ports_flat(
         name, property_string = label.string.split(':', 1)
         properties = property_string.split()
         ptype = properties[0] if len(properties) > 0 else 'unk'
-        angle_deg = float(properties[1]) if len(properties) > 1 else numpy.inf
+        if len(properties) > 1:
+            try:
+                angle_deg = float(properties[1])
+            except ValueError:
+                logger.warning(f'Invalid port label "{label.string}" in pattern "{pstr}" (bad angle)')
+                continue
+        else:
+            angle_deg = numpy.inf
 
         xy = label.offset
         angle = numpy.deg2rad(angle_deg) if numpy.isfinite(angle_deg) else None