diff --git a/lib/galaxy/datatypes/converters/interval_to_coverage.py b/lib/galaxy/datatypes/converters/interval_to_coverage.py
index 93042b62bb3..47882f7be6a 100644
--- a/lib/galaxy/datatypes/converters/interval_to_coverage.py
+++ b/lib/galaxy/datatypes/converters/interval_to_coverage.py
@@ -133,7 +133,7 @@ if __name__ == "__main__":
     temp_file = tempfile.NamedTemporaryFile(mode="r")
     environ['LC_ALL'] = 'POSIX'
     commandline = "sort -f -n -k %d -k %d -k %d -o %s %s" % (chr_col_1 + 1, start_col_1 + 1, end_col_1 + 1, temp_file.name, in_fname)
-    errorcode, stdout = subprocess.check_call(commandline, shell=True)
+    subprocess.check_call(commandline, shell=True)
 
     coverage = CoverageWriter( out_stream=open(out_fname, "a"),
                                chromCol=chr_col_2, positionCol=position_col_2,