diff --git a/LEGO1/mxregion.cpp b/LEGO1/mxregion.cpp
index bd2a5f5a..bacff021 100644
--- a/LEGO1/mxregion.cpp
+++ b/LEGO1/mxregion.cpp
@@ -107,7 +107,8 @@ MxBool MxRegion::vtable1c(MxRect32& p_rect)
 	MxRegionTopBottom* topBottom;
 
 	while (cursor.Next(topBottom)) {
-		if (topBottom->m_top >= p_rect.m_bottom)
+		MxS32 top = topBottom->m_top;
+		if ((topBottom->m_top = top) >= p_rect.m_bottom)
 			return FALSE;
 		if (topBottom->m_bottom > p_rect.m_top && topBottom->FUN_100c57b0(p_rect))
 			return TRUE;