Index: /trunk/psModules/src/detrend/pmBias.c
===================================================================
--- /trunk/psModules/src/detrend/pmBias.c	(revision 12646)
+++ /trunk/psModules/src/detrend/pmBias.c	(revision 12647)
@@ -79,9 +79,11 @@
 
     if ((inImage->numCols + x0in - x0sub) > subImage->numCols) {
-        psError(PS_ERR_UNKNOWN, true, "Image does not have enough columns for subtraction.\n");
+        psError(PS_ERR_UNKNOWN, true, "Image does not have enough columns for subtraction (%d vs %d).\n",
+                inImage->numCols + x0in - x0sub, subImage->numCols);
         return false;
     }
     if ((inImage->numRows + y0in - y0sub) > subImage->numRows) {
-        psError(PS_ERR_UNKNOWN, true, "Image does not have enough rows for subtraction.\n");
+        psError(PS_ERR_UNKNOWN, true, "Image does not have enough rows for subtraction (%d vs %d).\n",
+                inImage->numRows + y0in - y0sub, subImage->numRows);
         return false;
     }