diff --git a/src/cal_tools/calcat_interface2.py b/src/cal_tools/calcat_interface2.py
index 0cefef46a836bac4cb894f6e286ef24a4d45359a..ff4b893110bd278d901d4da54f2481ea1a27fd94 100644
--- a/src/cal_tools/calcat_interface2.py
+++ b/src/cal_tools/calcat_interface2.py
@@ -284,6 +284,10 @@ class CalibrationData(Mapping):
     def __len__(self):
         return len(self.constant_groups)
 
+    def __repr__(self):
+        return (f"<CalibrationData: {', '.join(sorted(self.constant_groups))} "
+                f"constants for {len(self.aggregators)} modules>")
+
     @property
     def module_nums(self):
         return [int(da[-2:]) for da in self.aggregators]