Index: trunk/psphot/src/psphotSourceSize.c
===================================================================
--- trunk/psphot/src/psphotSourceSize.c	(revision 18868)
+++ trunk/psphot/src/psphotSourceSize.c	(revision 18870)
@@ -212,8 +212,12 @@
     }
 
-    if (grow > 0 && !psImageConvolveMask(readout->mask, readout->mask, crMask, crMask,
-                                         -grow, grow, -grow, grow)) {
-        psError(PS_ERR_UNKNOWN, false, "Unable to grow CR mask");
-        return false;
+    if (grow > 0) {
+        psImage *newMask = psImageConvolveMask(NULL, readout->mask, crMask, crMask, -grow, grow, -grow, grow);
+        if (!newMask) {
+            psError(PS_ERR_UNKNOWN, false, "Unable to grow CR mask");
+            return false;
+        }
+        psFree(readout->mask);
+        readout->mask = newMask;
     }