Index: trunk/pswarp/src/pswarpTransformTile.c
===================================================================
--- trunk/pswarp/src/pswarpTransformTile.c	(revision 23487)
+++ trunk/pswarp/src/pswarpTransformTile.c	(revision 27096)
@@ -98,5 +98,5 @@
             psImageMaskType maskValue = inMaskData ? inMaskData[(int)yIn][(int)xIn] : 0; // Value of mask
             if (!psImageInterpolate(&imageValue, &varValue, &maskValue, xIn, yIn, args->interp)) {
-                psError(PS_ERR_UNKNOWN, false, "Unable to interpolate image.");
+                psError(psErrorCodeLast(), false, "Unable to interpolate image.");
                 return false;
             }