diff --git a/python/lsst/ip/diffim/subtractImages.py b/python/lsst/ip/diffim/subtractImages.py
index 6f8e9db5..3802c646 100644
--- a/python/lsst/ip/diffim/subtractImages.py
+++ b/python/lsst/ip/diffim/subtractImages.py
@@ -822,7 +822,8 @@ def _sourceSelector(self, sources, mask):
             self.log.error("Too few sources to calculate the PSF matching kernel: "
                            "%i selected but %i needed for the calculation.",
                            len(selectSources), self.config.minKernelSources)
-            raise RuntimeError("Cannot compute PSF matching kernel: too few sources selected.")
+            if not self.config.allowKernelSourceDetection:
+                raise RuntimeError("Cannot compute PSF matching kernel: too few sources selected.")
         self.metadata["nPsfSources"] = len(selectSources)
 
         return selectSources