diff --git a/src/gui.c b/src/gui.c
index 6154b48..b961108 100644
--- a/src/gui.c
+++ b/src/gui.c
@@ -2753,7 +2753,8 @@
 	}
 	else if (enc_utf8)
 	{
-	    if (ScreenLines[off + col1] == 0)
+	    // FIXME: how can the first character ever be zero?
+	    if (col1 > 0 && ScreenLines[off + col1] == 0)
 		--col1;
 # ifdef FEAT_GUI_GTK
 	    if (col2 + 1 < Columns && ScreenLines[off + col2 + 1] == 0)