diff --git a/src/p_ceiling.cpp b/src/p_ceiling.cpp
index fcd2a5487..fb324b54a 100644
--- a/src/p_ceiling.cpp
+++ b/src/p_ceiling.cpp
@@ -593,8 +593,9 @@ bool EV_CeilingCrushStop (int tag, bool remove)
 
 bool EV_StopCeiling(int tag, line_t *line)
 {
+	int sec;
 	FSectorTagIterator it(tag, line);
-	while (int sec = it.Next())
+	while ((sec = it.Next()) >= 0)
 	{
 		if (level.sectors[sec].ceilingdata)
 		{
diff --git a/src/p_floor.cpp b/src/p_floor.cpp
index 63ebdc4af..d0b6cb077 100644
--- a/src/p_floor.cpp
+++ b/src/p_floor.cpp
@@ -570,8 +570,9 @@ bool EV_FloorCrushStop (int tag, line_t *line)
 // same as above but stops any floor mover that was active on the given sector.
 bool EV_StopFloor(int tag, line_t *line)
 {
+	int sec;
 	FSectorTagIterator it(tag, line);
-	while (int sec = it.Next())
+	while ((sec = it.Next()) >= 0)
 	{
 		if (level.sectors[sec].floordata)
 		{