diff --git a/python/lsst/ip/diffim/subtractImages.py b/python/lsst/ip/diffim/subtractImages.py
index d01b53eda..b8160d6ff 100644
--- a/python/lsst/ip/diffim/subtractImages.py
+++ b/python/lsst/ip/diffim/subtractImages.py
@@ -668,10 +668,14 @@ def _calculateMagLim(self, exposure, nsigma=5.0, fallbackPsfSize=None):
         """
         if exposure.photoCalib is None:
             return np.nan
+        # Set maglim to nan upfront in case on an unexpected RuntimeError
+        maglim = np.nan
         try:
             psf = exposure.getPsf()
             psf_shape = psf.computeShape(psf.getAveragePosition())
-        except (lsst.pex.exceptions.InvalidParameterError, afwDetection.InvalidPsfError):
+        except (lsst.pex.exceptions.InvalidParameterError,
+                afwDetection.InvalidPsfError,
+                lsst.pex.exceptions.RangeError):
             if fallbackPsfSize is not None:
                 self.log.info("Unable to evaluate PSF, using fallback FWHM %f", fallbackPsfSize)
                 psf_area = np.pi*(fallbackPsfSize/2)**2