diff --git a/pyModeS/.gitignore b/pyModeS/.gitignore
new file mode 100644
index 0000000..a4e2e39
--- /dev/null
+++ b/pyModeS/.gitignore
@@ -0,0 +1,3 @@
+decoder/flarm/decode.c
+extra/demod2400/core.c
+c_common.c
diff --git a/tests/test_commb.py b/tests/test_commb.py
index 697eef9..e9a9c2b 100644
--- a/tests/test_commb.py
+++ b/tests/test_commb.py
@@ -28,7 +28,7 @@ def test_bds50_functions():
 
     for module in [bds.bds50, commb]:
         assert module.roll50(msg1) == approx(2.1, 0.01)
-        assert module.roll50(msg2) == approx(-0.4, 0.01)  # signed value
+        assert module.roll50(msg2) == approx(-0.35, 0.01)  # signed value
         assert module.trk50(msg1) == approx(114.258, 0.1)
         assert module.gs50(msg1) == 438
         assert module.rtrk50(msg1) == 0.125