diff --git a/src/p_maputl.cpp b/src/p_maputl.cpp
index 526626b22..b55989c97 100644
--- a/src/p_maputl.cpp
+++ b/src/p_maputl.cpp
@@ -833,6 +833,7 @@ bool FMultiBlockLinesIterator::Next(FMultiBlockLinesIterator::CheckResult *item)
 	}
 	if (onlast)
 	{
+		cursector = startsector;
 		// We reached the end of the list. Check if we still need to check up- and downwards.
 		if (GoUp(checkpoint.x, checkpoint.y) ||
 			GoDown(checkpoint.x, checkpoint.y))