Index: trunk/psphot/src/psphotImageBackground.c
===================================================================
--- trunk/psphot/src/psphotImageBackground.c	(revision 5672)
+++ trunk/psphot/src/psphotImageBackground.c	(revision 5718)
@@ -58,7 +58,5 @@
     for (int j = 0; j < image->numRows; j++) {
 	for (int i = 0; i < image->numCols; i++) {
-	    if (mask->data.U8[j][i]) {
-		image->data.F32[j][i] = 0;
-	    } else {
+	    if (!mask->data.U8[j][i]) {
 		Sky = psPolynomial2DEval (skyModel, i, j);
 		image->data.F32[j][i] -= Sky;
@@ -66,4 +64,5 @@
 	}
     }
+
     psLogMsg ("psphot", 5, "back: %f sec (fit model)\n", psTimerMark ("psphot"));