Index: trunk/psModules/src/imcombine/pmSubtraction.c
===================================================================
--- trunk/psModules/src/imcombine/pmSubtraction.c	(revision 21457)
+++ trunk/psModules/src/imcombine/pmSubtraction.c	(revision 21469)
@@ -1353,4 +1353,7 @@
         out1->covariance = psImageCovarianceCalculate(kernel, ro1->covariance);
         psFree(kernel);
+        if (out1->variance) {
+            psImageCovarianceTransfer(out1->variance, out1->covariance);
+        }
     }
     if (kernels->mode == PM_SUBTRACTION_MODE_2 || kernels->mode == PM_SUBTRACTION_MODE_DUAL) {
@@ -1359,4 +1362,7 @@
         out2->covariance = psImageCovarianceCalculate(kernel, ro2->covariance);
         psFree(kernel);
+        if (out2->variance) {
+            psImageCovarianceTransfer(out2->variance, out2->covariance);
+        }
     }