diff --git a/CHANGES.rst b/CHANGES.rst
index f9ef142..dd944aa 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -34,6 +34,9 @@ Bug Fixes
   were set to the number of rows in the image, biasing the final fit to all bin
   peaks. Previously for Gaussian, the entire fit failed. [#205, #206]
 
+- Fixed input of `traces` in `Background`. Added a condition to 'FlatTrace' that
+  trace position must be a positive number. [#211]
+
 Other changes
 ^^^^^^^^^^^^^
 
diff --git a/specreduce/tests/test_background.py b/specreduce/tests/test_background.py
index d188f98..3162f4b 100644
--- a/specreduce/tests/test_background.py
+++ b/specreduce/tests/test_background.py
@@ -125,7 +125,7 @@ def test_trace_inputs(mk_test_img_raw):
     assert isinstance(background.traces[0], FlatTrace)
     assert background.traces[0].trace_pos == 10.
 
-    traces = [10., 12]
+    traces = [10., 15]
     background = Background(image, traces, width=5)
     for i, trace_pos in enumerate(traces):
         assert background.traces[i].trace_pos == trace_pos