Index: trunk/ppStats/src/ppStatsReadout.c
===================================================================
--- trunk/ppStats/src/ppStatsReadout.c	(revision 15374)
+++ trunk/ppStats/src/ppStatsReadout.c	(revision 17221)
@@ -71,8 +71,9 @@
             int x = j % image->numCols;
             sampleValues->data.F32[i] = image->data.F32[y][x];
-            if (mask && (!mask->data.PS_TYPE_MASK_DATA[y][x] & data->maskVal) &&
+            if ((!mask || !(mask->data.PS_TYPE_MASK_DATA[y][x] & data->maskVal)) &&
                 !isfinite(sampleValues->data.F32[i])) {
                 if (!warnNonFinite) {
-                    psWarning("Unmasked non-finite value detected at %d,%d", x, y);
+                    psWarning("Unmasked non-finite value detected at %d,%d; "
+                              "further warnings will be suppressed", x, y);
                     warnNonFinite = true;
                 }