Index: trunk/src/tool_line.c
===================================================================
--- trunk/src/tool_line.c	(revision 13502)
+++ trunk/src/tool_line.c	(revision 13503)
@@ -350,7 +350,7 @@
 		/* save both ends of line */
 		pcb_crosshair.AttachedLine.Point2.X = ptr2->Point1.X;
 		pcb_crosshair.AttachedLine.Point2.Y = ptr2->Point1.Y;
-		if ((type = pcb_undo(pcb_true)))
+		if ((type = pcb_undo(pcb_true)) == 0)
 			pcb_board_set_changed_flag(pcb_true);
 		/* check that the undo was of the right type */
 		if ((type & PCB_UNDO_CREATE) == 0) {
Index: trunk/src/undo.c
===================================================================
--- trunk/src/undo.c	(revision 13502)
+++ trunk/src/undo.c	(revision 13503)
@@ -89,12 +89,12 @@
 
 	if (pcb_uundo.num_undo == 0) {
 		pcb_message(PCB_MSG_INFO, _("Nothing to undo - buffer is empty\n"));
-		return 0;
+		return -1;
 	}
 
 	if (pcb_uundo.serial == 0) {
 		pcb_message(PCB_MSG_ERROR, _("ERROR: Attempt to pcb_undo() with Serial == 0\n" "       Please save your work and report this bug.\n"));
-		return 0;
+		return -1;
 	}
 
 	if ((pcb_uundo.tail != NULL) && (pcb_uundo.tail->serial > pcb_uundo.serial)) {
@@ -109,7 +109,7 @@
 		 * the problem and  allow the user to hit Undo again.
 		 */
 		pcb_uundo.serial = pcb_uundo.tail->serial + 1;
-		return 0;
+		return -1;
 	}
 
 	pcb_undo_lock(); /* lock undo module to prevent from loops */
Index: trunk/src/undo_act.c
===================================================================
--- trunk/src/undo_act.c	(revision 13502)
+++ trunk/src/undo_act.c	(revision 13503)
@@ -132,7 +132,7 @@
 	if (!function || !*function) {
 		pcb_notify_crosshair_change(pcb_false);
 		if (pcb_tool_undo_act())
-			if (pcb_undo(pcb_true))
+			if (pcb_undo(pcb_true) == 0)
 				pcb_board_set_changed_flag(pcb_true);
 	}
 	else if (function) {