diff --git a/st.c b/st.c
index e55e7b3..6f40e35 100644
--- a/st.c
+++ b/st.c
@@ -965,6 +965,9 @@ tsetdirt(int top, int bot)
 {
 	int i;
 
+	if (term.row <= 0)
+		return;
+
 	LIMIT(top, 0, term.row-1);
 	LIMIT(bot, 0, term.row-1);