diff --git a/geomagio/covjson/CovJSONFactory.py b/geomagio/covjson/CovJSONFactory.py
index 02088e52add3870b1791578fc791e098263bde84..401ca653ae42ad0d172a480c77b6e2f846110258 100644
--- a/geomagio/covjson/CovJSONFactory.py
+++ b/geomagio/covjson/CovJSONFactory.py
@@ -249,6 +249,8 @@ class CovJSONFactory(TimeseriesFactory):
 
         for trace in timeseries:
             ch_name = trace.stats.channel
+            if channels and ch_name not in channels:
+                continue
             element_info = ELEMENT_INDEX.get(ch_name)
             if element_info:
                 param_description = element_info.name