diff --git a/src/screen.c b/src/screen.c
index 0d65b4b..86ebd40 100644
--- a/src/screen.c
+++ b/src/screen.c
@@ -464,7 +464,8 @@
     // First char of a popup window may go on top of the right half of a
     // double-wide character. Clear the left half to avoid it getting the popup
     // window background color.
-    if (coloff > 0 && ScreenLines[off_to] == 0)
+    if (coloff > 0 && ScreenLines[off_to] == 0
+					     && ScreenLinesUC[off_to - 1] != 0)
     {
 	ScreenLines[off_to - 1] = ' ';
 	ScreenLinesUC[off_to - 1] = 0;