diff --git a/wcs_olap/tb.py b/wcs_olap/tb.py
index 8a9ec1d..1f7d293 100644
--- a/wcs_olap/tb.py
+++ b/wcs_olap/tb.py
@@ -52,4 +52,4 @@ def print_tb():
         tb = tb.tb_next
         n = n + 1
 
-    print error_file.getvalue()
+    print >>sys.stderr, error_file.getvalue()