diff --git a/python/lsst/ip/diffim/subtractImages.py b/python/lsst/ip/diffim/subtractImages.py
index 8cf0f76be..d6afc3365 100644
--- a/python/lsst/ip/diffim/subtractImages.py
+++ b/python/lsst/ip/diffim/subtractImages.py
@@ -794,6 +794,9 @@ def _sourceSelector(self, sources, mask):
             remaining after source selection.
         """
 
+        # Ensure the source catalog is contiguous before making any cuts
+        if not sources.isContiguous():
+            sources = sources.copy(deep=True)
         selected = self.sourceSelector.selectSources(sources).selected
         nInitialSelected = np.count_nonzero(selected)
         selected *= self._checkMask(mask, sources, self.config.excludeMaskPlanes)