diff --git a/python/lsst/ip/diffim/detectAndMeasure.py b/python/lsst/ip/diffim/detectAndMeasure.py
index 03ed20da7..8b7184568 100644
--- a/python/lsst/ip/diffim/detectAndMeasure.py
+++ b/python/lsst/ip/diffim/detectAndMeasure.py
@@ -804,7 +804,7 @@ def processResults(self, science, matchedTemplate, difference, sources, idFactor
         measurementResults.subtractedMeasuredExposure = difference
 
         if self.config.doMaskStreaks and self.config.writeStreakInfo:
-            measurementResults.mergeItems(streakInfo, 'maskedStreaks')
+            measurementResults.maskedStreaks = streakInfo.maskedStreaks
 
         if kernelSources is not None:
             self.calculateMetrics(science, difference, diaSources, kernelSources)