diff --git a/python/lsst/ap/association/metrics.py b/python/lsst/ap/association/metrics.py
index 316c2349..cf0126af 100644
--- a/python/lsst/ap/association/metrics.py
+++ b/python/lsst/ap/association/metrics.py
@@ -326,8 +326,10 @@ def makeMeasurement(self, dbHandle, outputDataId):
         ValueError
             Raised if outputDataId is not empty
         """
-        # All data ID types define keys()
-        if outputDataId.keys() - {'instrument'}:
+        # DataCoordinate objects are not mappings, so they don't have keys(),
+        # but their .required attribute is a mapping.
+        mapping = getattr(outputDataId, "required", outputDataId)
+        if mapping.keys() - {'instrument'}:
             raise ValueError("%s must not be associated with specific data IDs (gave %s)."
                              % (self.config.metricName, outputDataId))