Index: trunk/psModules/src/imcombine/pmSubtractionMatch.c
===================================================================
--- trunk/psModules/src/imcombine/pmSubtractionMatch.c	(revision 14805)
+++ trunk/psModules/src/imcombine/pmSubtractionMatch.c	(revision 14835)
@@ -128,4 +128,8 @@
             PS_ASSERT_IMAGES_SIZE_EQUAL(input->weight, reference->image, false);
         }
+    } else if (!stampsName && !sources) {
+        psError(PS_ERR_UNEXPECTED_NULL, true,
+                "A list of sources is required for convolving to a target PSF.");
+        return false;
     }
     PS_ASSERT_INT_NONNEGATIVE(footprint, false);